The Tor Browser: gfx/qcms/iccread.c@97036ab72558 (annotated)

gfx/qcms/iccread.c@97036ab72558 (annotated)

gfx/qcms/iccread.c

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* vim: set ts=8 sw=8 noexpandtab: */
 //  qcms
 //  Copyright (C) 2009 Mozilla Foundation
 //  Copyright (C) 1998-2007 Marti Maria
 //
 // Permission is hereby granted, free of charge, to any person obtaining
 // a copy of this software and associated documentation files (the "Software"),
 // to deal in the Software without restriction, including without limitation
 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
 // and/or sell copies of the Software, and to permit persons to whom the Software
 // is furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
 // THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <math.h>
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h> //memset
 #include "qcmsint.h"
 /* It might be worth having a unified limit on content controlled
  * allocation per profile. This would remove the need for many
  * of the arbitrary limits that we used */
 typedef uint32_t be32;
 typedef uint16_t be16;
 static be32 cpu_to_be32(uint32_t v)
 {
 #ifdef IS_LITTLE_ENDIAN
 	return ((v & 0xff) << 24) | ((v & 0xff00) << 8) | ((v & 0xff0000) >> 8) | ((v & 0xff000000) >> 24);
 #else
 	return v;
 #endif
 }
 static be16 cpu_to_be16(uint16_t v)
 {
 #ifdef IS_LITTLE_ENDIAN
 	return ((v & 0xff) << 8) | ((v & 0xff00) >> 8);
 #else
 	return v;
 #endif
 }
 static uint32_t be32_to_cpu(be32 v)
 {
 #ifdef IS_LITTLE_ENDIAN
 	return ((v & 0xff) << 24) | ((v & 0xff00) << 8) | ((v & 0xff0000) >> 8) | ((v & 0xff000000) >> 24);
 	//return __builtin_bswap32(v);
 #else
 	return v;
 #endif
 }
 static uint16_t be16_to_cpu(be16 v)
 {
 #ifdef IS_LITTLE_ENDIAN
 	return ((v & 0xff) << 8) | ((v & 0xff00) >> 8);
 #else
 	return v;
 #endif
 }
 /* a wrapper around the memory that we are going to parse
  * into a qcms_profile */
 struct mem_source
 {
 	const unsigned char *buf;
 	size_t size;
 	qcms_bool valid;
 	const char *invalid_reason;
 };
 static void invalid_source(struct mem_source *mem, const char *reason)
 {
 	mem->valid = false;
 	mem->invalid_reason = reason;
 }
 static uint32_t read_u32(struct mem_source *mem, size_t offset)
 {
 	/* Subtract from mem->size instead of the more intuitive adding to offset.
 	 * This avoids overflowing offset. The subtraction is safe because
 	 * mem->size is guaranteed to be > 4 */
 	if (offset > mem->size - 4) {
 		invalid_source(mem, "Invalid offset");
 		return 0;
 	} else {
 		be32 k;
 		memcpy(&k, mem->buf + offset, sizeof(k));
 		return be32_to_cpu(k);
 	}
 }
 static uint16_t read_u16(struct mem_source *mem, size_t offset)
 {
 	if (offset > mem->size - 2) {
 		invalid_source(mem, "Invalid offset");
 		return 0;
 	} else {
 		be16 k;
 		memcpy(&k, mem->buf + offset, sizeof(k));
 		return be16_to_cpu(k);
 	}
 }
 static uint8_t read_u8(struct mem_source *mem, size_t offset)
 {
 	if (offset > mem->size - 1) {
 		invalid_source(mem, "Invalid offset");
 		return 0;
 	} else {
 		return *(uint8_t*)(mem->buf + offset);
 	}
 }
 static s15Fixed16Number read_s15Fixed16Number(struct mem_source *mem, size_t offset)
 {
 	return read_u32(mem, offset);
 }
 static uInt8Number read_uInt8Number(struct mem_source *mem, size_t offset)
 {
 	return read_u8(mem, offset);
 }
 static uInt16Number read_uInt16Number(struct mem_source *mem, size_t offset)
 {
 	return read_u16(mem, offset);
 }
 static void write_u32(void *mem, size_t offset, uint32_t value)
 {
     *((uint32_t *)((unsigned char*)mem + offset)) = cpu_to_be32(value);
 }
 static void write_u16(void *mem, size_t offset, uint16_t value)
 {
     *((uint16_t *)((unsigned char*)mem + offset)) = cpu_to_be16(value);
 }
 #define BAD_VALUE_PROFILE NULL
 #define INVALID_PROFILE NULL
 #define NO_MEM_PROFILE NULL
 /* An arbitrary 4MB limit on profile size */
 #define MAX_PROFILE_SIZE 1024*1024*4
 #define MAX_TAG_COUNT 1024
 static void check_CMM_type_signature(struct mem_source *src)
 {
 	//uint32_t CMM_type_signature = read_u32(src, 4);
 	//TODO: do the check?
 }
 static void check_profile_version(struct mem_source *src)
 {
 	/*
 	uint8_t major_revision = read_u8(src, 8 + 0);
 	uint8_t minor_revision = read_u8(src, 8 + 1);
 	*/
 	uint8_t reserved1      = read_u8(src, 8 + 2);
 	uint8_t reserved2      = read_u8(src, 8 + 3);
 	/* Checking the version doesn't buy us anything
 	if (major_revision != 0x4) {
 		if (major_revision > 0x2)
 			invalid_source(src, "Unsupported major revision");
 		if (minor_revision > 0x40)
 			invalid_source(src, "Unsupported minor revision");
 	}
 	*/
 	if (reserved1 != 0 || reserved2 != 0)
 		invalid_source(src, "Invalid reserved bytes");
 }
 #define INPUT_DEVICE_PROFILE   0x73636e72 // 'scnr'
 #define DISPLAY_DEVICE_PROFILE 0x6d6e7472 // 'mntr'
 #define OUTPUT_DEVICE_PROFILE  0x70727472 // 'prtr'
 #define DEVICE_LINK_PROFILE    0x6c696e6b // 'link'
 #define COLOR_SPACE_PROFILE    0x73706163 // 'spac'
 #define ABSTRACT_PROFILE       0x61627374 // 'abst'
 #define NAMED_COLOR_PROFILE    0x6e6d636c // 'nmcl'
 static void read_class_signature(qcms_profile *profile, struct mem_source *mem)
 {
 	profile->class = read_u32(mem, 12);
 	switch (profile->class) {
 		case DISPLAY_DEVICE_PROFILE:
 		case INPUT_DEVICE_PROFILE:
 		case OUTPUT_DEVICE_PROFILE:
 		case COLOR_SPACE_PROFILE:
 			break;
 		default:
 			invalid_source(mem, "Invalid  Profile/Device Class signature");
 	}
 }
 static void read_color_space(qcms_profile *profile, struct mem_source *mem)
 {
 	profile->color_space = read_u32(mem, 16);
 	switch (profile->color_space) {
 		case RGB_SIGNATURE:
 		case GRAY_SIGNATURE:
 			break;
 		default:
 			invalid_source(mem, "Unsupported colorspace");
 	}
 }
 static void read_pcs(qcms_profile *profile, struct mem_source *mem)
 {
 	profile->pcs = read_u32(mem, 20);
 	switch (profile->pcs) {
 		case XYZ_SIGNATURE:
 		case LAB_SIGNATURE:
 			break;
 		default:
 			invalid_source(mem, "Unsupported pcs");
 	}
 }
 struct tag
 {
 	uint32_t signature;
 	uint32_t offset;
 	uint32_t size;
 };
 struct tag_index {
 	uint32_t count;
 	struct tag *tags;
 };
 static struct tag_index read_tag_table(qcms_profile *profile, struct mem_source *mem)
 {
 	struct tag_index index = {0, NULL};
 	unsigned int i;
 	index.count = read_u32(mem, 128);
 	if (index.count > MAX_TAG_COUNT) {
 		invalid_source(mem, "max number of tags exceeded");
 		return index;
 	}
 	index.tags = malloc(sizeof(struct tag)*index.count);
 	if (index.tags) {
 		for (i = 0; i < index.count; i++) {
 			index.tags[i].signature = read_u32(mem, 128 + 4 + 4*i*3);
 			index.tags[i].offset    = read_u32(mem, 128 + 4 + 4*i*3 + 4);
 			index.tags[i].size      = read_u32(mem, 128 + 4 + 4*i*3 + 8);
 		}
 	}
 	return index;
 }
 // Checks a profile for obvious inconsistencies and returns
 // true if the profile looks bogus and should probably be
 // ignored.
 qcms_bool qcms_profile_is_bogus(qcms_profile *profile)
 {
        float sum[3], target[3], tolerance[3];
        float rX, rY, rZ, gX, gY, gZ, bX, bY, bZ;
        bool negative;
        unsigned i;
        // We currently only check the bogosity of RGB profiles
        if (profile->color_space != RGB_SIGNATURE)
 	       return false;
        if (profile->A2B0 || profile->B2A0)
                return false;
        rX = s15Fixed16Number_to_float(profile->redColorant.X);
        rY = s15Fixed16Number_to_float(profile->redColorant.Y);
        rZ = s15Fixed16Number_to_float(profile->redColorant.Z);
        gX = s15Fixed16Number_to_float(profile->greenColorant.X);
        gY = s15Fixed16Number_to_float(profile->greenColorant.Y);
        gZ = s15Fixed16Number_to_float(profile->greenColorant.Z);
        bX = s15Fixed16Number_to_float(profile->blueColorant.X);
        bY = s15Fixed16Number_to_float(profile->blueColorant.Y);
        bZ = s15Fixed16Number_to_float(profile->blueColorant.Z);
        // Check if any of the XYZ values are negative (see mozilla bug 498245)
        // CIEXYZ tristimulus values cannot be negative according to the spec.
        negative =
 	       (rX < 0) || (rY < 0) || (rZ < 0) ||
 	       (gX < 0) || (gY < 0) || (gZ < 0) ||
 	       (bX < 0) || (bY < 0) || (bZ < 0);
        if (negative)
 	       return true;
        // Sum the values; they should add up to something close to white
        sum[0] = rX + gX + bX;
        sum[1] = rY + gY + bY;
        sum[2] = rZ + gZ + bZ;
        // Build our target vector (see mozilla bug 460629)
        target[0] = 0.96420;
        target[1] = 1.00000;
        target[2] = 0.82491;
        // Our tolerance vector - Recommended by Chris Murphy based on
        // conversion from the LAB space criterion of no more than 3 in any one
        // channel. This is similar to, but slightly more tolerant than Adobe's
        // criterion.
        tolerance[0] = 0.02;
        tolerance[1] = 0.02;
        tolerance[2] = 0.04;
        // Compare with our tolerance
        for (i = 0; i < 3; ++i) {
            if (!(((sum[i] - tolerance[i]) <= target[i]) &&
                  ((sum[i] + tolerance[i]) >= target[i])))
                return true;
        }
        // All Good
        return false;
 }
 #define TAG_bXYZ 0x6258595a
 #define TAG_gXYZ 0x6758595a
 #define TAG_rXYZ 0x7258595a
 #define TAG_rTRC 0x72545243
 #define TAG_bTRC 0x62545243
 #define TAG_gTRC 0x67545243
 #define TAG_kTRC 0x6b545243
 #define TAG_A2B0 0x41324230
 #define TAG_B2A0 0x42324130
 #define TAG_CHAD 0x63686164
 static struct tag *find_tag(struct tag_index index, uint32_t tag_id)
 {
 	unsigned int i;
 	struct tag *tag = NULL;
 	for (i = 0; i < index.count; i++) {
 		if (index.tags[i].signature == tag_id) {
 			return &index.tags[i];
 		}
 	}
 	return tag;
 }
 #define XYZ_TYPE		0x58595a20 // 'XYZ '
 #define CURVE_TYPE		0x63757276 // 'curv'
 #define PARAMETRIC_CURVE_TYPE	0x70617261 // 'para'
 #define LUT16_TYPE		0x6d667432 // 'mft2'
 #define LUT8_TYPE		0x6d667431 // 'mft1'
 #define LUT_MAB_TYPE		0x6d414220 // 'mAB '
 #define LUT_MBA_TYPE		0x6d424120 // 'mBA '
 #define CHROMATIC_TYPE		0x73663332 // 'sf32'
 static struct matrix read_tag_s15Fixed16ArrayType(struct mem_source *src, struct tag_index index, uint32_t tag_id)
 {
 	struct tag *tag = find_tag(index, tag_id);
 	struct matrix matrix;
 	if (tag) {
 		uint8_t i;
 		uint32_t offset = tag->offset;
 		uint32_t type = read_u32(src, offset);
 		// Check mandatory type signature for s16Fixed16ArrayType
 		if (type != CHROMATIC_TYPE) {
 			invalid_source(src, "unexpected type, expected 'sf32'");
 		}
 		for (i = 0; i < 9; i++) {
 			matrix.m[i/3][i%3] = s15Fixed16Number_to_float(read_s15Fixed16Number(src, offset+8+i*4));
 		}
 		matrix.invalid = false;
 	} else {
 		matrix.invalid = true;
 		invalid_source(src, "missing sf32tag");
 	}
 	return matrix;
 }
 static struct XYZNumber read_tag_XYZType(struct mem_source *src, struct tag_index index, uint32_t tag_id)
 {
 	struct XYZNumber num = {0, 0, 0};
 	struct tag *tag = find_tag(index, tag_id);
 	if (tag) {
 		uint32_t offset = tag->offset;
 		uint32_t type = read_u32(src, offset);
 		if (type != XYZ_TYPE)
 			invalid_source(src, "unexpected type, expected XYZ");
 		num.X = read_s15Fixed16Number(src, offset+8);
 		num.Y = read_s15Fixed16Number(src, offset+12);
 		num.Z = read_s15Fixed16Number(src, offset+16);
 	} else {
 		invalid_source(src, "missing xyztag");
 	}
 	return num;
 }
 // Read the tag at a given offset rather then the tag_index.
 // This method is used when reading mAB tags where nested curveType are
 // present that are not part of the tag_index.
 static struct curveType *read_curveType(struct mem_source *src, uint32_t offset, uint32_t *len)
 {
 	static const uint32_t COUNT_TO_LENGTH[5] = {1, 3, 4, 5, 7};
 	struct curveType *curve = NULL;
 	uint32_t type = read_u32(src, offset);
 	uint32_t count;
 	uint32_t i;
 	if (type != CURVE_TYPE && type != PARAMETRIC_CURVE_TYPE) {
 		invalid_source(src, "unexpected type, expected CURV or PARA");
 		return NULL;
 	}
 	if (type == CURVE_TYPE) {
 		count = read_u32(src, offset+8);
 #define MAX_CURVE_ENTRIES 40000 //arbitrary
 		if (count > MAX_CURVE_ENTRIES) {
 			invalid_source(src, "curve size too large");
 			return NULL;
 		}
 		curve = malloc(sizeof(struct curveType) + sizeof(uInt16Number)*count);
 		if (!curve)
 			return NULL;
 		curve->count = count;
 		curve->type = CURVE_TYPE;
 		for (i=0; i<count; i++) {
 			curve->data[i] = read_u16(src, offset + 12 + i*2);
 		}
 		*len = 12 + count * 2;
 	} else { //PARAMETRIC_CURVE_TYPE
 		count = read_u16(src, offset+8);
 		if (count > 4) {
 			invalid_source(src, "parametric function type not supported.");
 			return NULL;
 		}
 		curve = malloc(sizeof(struct curveType));
 		if (!curve)
 			return NULL;
 		curve->count = count;
 		curve->type = PARAMETRIC_CURVE_TYPE;
 		for (i=0; i < COUNT_TO_LENGTH[count]; i++) {
 			curve->parameter[i] = s15Fixed16Number_to_float(read_s15Fixed16Number(src, offset + 12 + i*4));
 		}
 		*len = 12 + COUNT_TO_LENGTH[count] * 4;
 		if ((count == 1 || count == 2)) {
 			/* we have a type 1 or type 2 function that has a division by 'a' */
 			float a = curve->parameter[1];
 			if (a == 0.f)
 				invalid_source(src, "parametricCurve definition causes division by zero.");
 		}
 	}
 	return curve;
 }
 static struct curveType *read_tag_curveType(struct mem_source *src, struct tag_index index, uint32_t tag_id)
 {
 	struct tag *tag = find_tag(index, tag_id);
 	struct curveType *curve = NULL;
 	if (tag) {
 		uint32_t len;
 		return read_curveType(src, tag->offset, &len);
 	} else {
 		invalid_source(src, "missing curvetag");
 	}
 	return curve;
 }
 #define MAX_CLUT_SIZE 500000 // arbitrary
 #define MAX_CHANNELS 10 // arbitrary
 static void read_nested_curveType(struct mem_source *src, struct curveType *(*curveArray)[MAX_CHANNELS], uint8_t num_channels, uint32_t curve_offset)
 {
 	uint32_t channel_offset = 0;
 	int i;
 	for (i = 0; i < num_channels; i++) {
 		uint32_t tag_len;
 		(*curveArray)[i] = read_curveType(src, curve_offset + channel_offset, &tag_len);
 		if (!(*curveArray)[i]) {
 			invalid_source(src, "invalid nested curveType curve");
 		}
 		channel_offset += tag_len;
 		// 4 byte aligned
 		if ((tag_len % 4) != 0)
 			channel_offset += 4 - (tag_len % 4);
 	}
 }
 static void mAB_release(struct lutmABType *lut)
 {
 	uint8_t i;
 	for (i = 0; i < lut->num_in_channels; i++){
 		free(lut->a_curves[i]);
 	}
 	for (i = 0; i < lut->num_out_channels; i++){
 		free(lut->b_curves[i]);
 		free(lut->m_curves[i]);
 	}
 	free(lut);
 }
 /* See section 10.10 for specs */
 static struct lutmABType *read_tag_lutmABType(struct mem_source *src, struct tag_index index, uint32_t tag_id)
 {
 	struct tag *tag = find_tag(index, tag_id);
 	uint32_t offset = tag->offset;
 	uint32_t a_curve_offset, b_curve_offset, m_curve_offset;
 	uint32_t matrix_offset;
 	uint32_t clut_offset;
 	uint32_t clut_size = 1;
 	uint8_t clut_precision;
 	uint32_t type = read_u32(src, offset);
 	uint8_t num_in_channels, num_out_channels;
 	struct lutmABType *lut;
 	uint32_t i;
 	if (type != LUT_MAB_TYPE && type != LUT_MBA_TYPE) {
 		return NULL;
 	}
 	num_in_channels = read_u8(src, offset + 8);
 	num_out_channels = read_u8(src, offset + 8);
 	if (num_in_channels > MAX_CHANNELS || num_out_channels > MAX_CHANNELS)
 		return NULL;
 	// We require 3in/out channels since we only support RGB->XYZ (or RGB->LAB)
 	// XXX: If we remove this restriction make sure that the number of channels
 	//      is less or equal to the maximum number of mAB curves in qcmsint.h
 	//      also check for clut_size overflow.
 	if (num_in_channels != 3 || num_out_channels != 3)
 		return NULL;
 	// some of this data is optional and is denoted by a zero offset
 	// we also use this to track their existance
 	a_curve_offset = read_u32(src, offset + 28);
 	clut_offset = read_u32(src, offset + 24);
 	m_curve_offset = read_u32(src, offset + 20);
 	matrix_offset = read_u32(src, offset + 16);
 	b_curve_offset = read_u32(src, offset + 12);
 	// Convert offsets relative to the tag to relative to the profile
 	// preserve zero for optional fields
 	if (a_curve_offset)
 		a_curve_offset += offset;
 	if (clut_offset)
 		clut_offset += offset;
 	if (m_curve_offset)
 		m_curve_offset += offset;
 	if (matrix_offset)
 		matrix_offset += offset;
 	if (b_curve_offset)
 		b_curve_offset += offset;
 	if (clut_offset) {
 		assert (num_in_channels == 3);
 		// clut_size can not overflow since lg(256^num_in_channels) = 24 bits.
 		for (i = 0; i < num_in_channels; i++) {
 			clut_size *= read_u8(src, clut_offset + i);
 		}
 	} else {
 		clut_size = 0;
 	}
 	// 24bits * 3 won't overflow either
 	clut_size = clut_size * num_out_channels;
 	if (clut_size > MAX_CLUT_SIZE)
 		return NULL;
 	lut = malloc(sizeof(struct lutmABType) + (clut_size) * sizeof(float));
 	if (!lut)
 		return NULL;
 	// we'll fill in the rest below
 	memset(lut, 0, sizeof(struct lutmABType));
 	lut->clut_table   = &lut->clut_table_data[0];
 	for (i = 0; i < num_in_channels; i++) {
 		lut->num_grid_points[i] = read_u8(src, clut_offset + i);
 	}
 	// Reverse the processing of transformation elements for mBA type.
 	lut->reversed = (type == LUT_MBA_TYPE);
 	lut->num_in_channels = num_in_channels;
 	lut->num_out_channels = num_out_channels;
 	if (matrix_offset) {
 		// read the matrix if we have it
 		lut->e00 = read_s15Fixed16Number(src, matrix_offset+4*0);
 		lut->e01 = read_s15Fixed16Number(src, matrix_offset+4*1);
 		lut->e02 = read_s15Fixed16Number(src, matrix_offset+4*2);
 		lut->e10 = read_s15Fixed16Number(src, matrix_offset+4*3);
 		lut->e11 = read_s15Fixed16Number(src, matrix_offset+4*4);
 		lut->e12 = read_s15Fixed16Number(src, matrix_offset+4*5);
 		lut->e20 = read_s15Fixed16Number(src, matrix_offset+4*6);
 		lut->e21 = read_s15Fixed16Number(src, matrix_offset+4*7);
 		lut->e22 = read_s15Fixed16Number(src, matrix_offset+4*8);
 		lut->e03 = read_s15Fixed16Number(src, matrix_offset+4*9);
 		lut->e13 = read_s15Fixed16Number(src, matrix_offset+4*10);
 		lut->e23 = read_s15Fixed16Number(src, matrix_offset+4*11);
 	}
 	if (a_curve_offset) {
 		read_nested_curveType(src, &lut->a_curves, num_in_channels, a_curve_offset);
 	}
 	if (m_curve_offset) {
 		read_nested_curveType(src, &lut->m_curves, num_out_channels, m_curve_offset);
 	}
 	if (b_curve_offset) {
 		read_nested_curveType(src, &lut->b_curves, num_out_channels, b_curve_offset);
 	} else {
 		invalid_source(src, "B curves required");
 	}
 	if (clut_offset) {
 		clut_precision = read_u8(src, clut_offset + 16);
 		if (clut_precision == 1) {
 			for (i = 0; i < clut_size; i++) {
 				lut->clut_table[i] = uInt8Number_to_float(read_uInt8Number(src, clut_offset + 20 + i*1));
 			}
 		} else if (clut_precision == 2) {
 			for (i = 0; i < clut_size; i++) {
 				lut->clut_table[i] = uInt16Number_to_float(read_uInt16Number(src, clut_offset + 20 + i*2));
 			}
 		} else {
 			invalid_source(src, "Invalid clut precision");
 		}
 	}
 	if (!src->valid) {
 		mAB_release(lut);
 		return NULL;
 	}
 	return lut;
 }
 static struct lutType *read_tag_lutType(struct mem_source *src, struct tag_index index, uint32_t tag_id)
 {
 	struct tag *tag = find_tag(index, tag_id);
 	uint32_t offset = tag->offset;
 	uint32_t type = read_u32(src, offset);
 	uint16_t num_input_table_entries;
 	uint16_t num_output_table_entries;
 	uint8_t in_chan, grid_points, out_chan;
 	uint32_t clut_offset, output_offset;
 	uint32_t clut_size;
 	size_t entry_size;
 	struct lutType *lut;
 	uint32_t i;
 	/* I'm not sure why the spec specifies a fixed number of entries for LUT8 tables even though
 	 * they have room for the num_entries fields */
 	if (type == LUT8_TYPE) {
 		num_input_table_entries = 256;
 		num_output_table_entries = 256;
 		entry_size = 1;
 	} else if (type == LUT16_TYPE) {
 		num_input_table_entries  = read_u16(src, offset + 48);
 		num_output_table_entries = read_u16(src, offset + 50);
 		entry_size = 2;
 	} else {
 		assert(0); // the caller checks that this doesn't happen
 		invalid_source(src, "Unexpected lut type");
 		return NULL;
 	}
 	in_chan     = read_u8(src, offset + 8);
 	out_chan    = read_u8(src, offset + 9);
 	grid_points = read_u8(src, offset + 10);
 	clut_size = pow(grid_points, in_chan);
 	if (clut_size > MAX_CLUT_SIZE) {
 		return NULL;
 	}
 	if (in_chan != 3 || out_chan != 3) {
 		return NULL;
 	}
 	lut = malloc(sizeof(struct lutType) + (num_input_table_entries * in_chan + clut_size*out_chan + num_output_table_entries * out_chan)*sizeof(float));
 	if (!lut) {
 		return NULL;
 	}
 	/* compute the offsets of tables */
 	lut->input_table  = &lut->table_data[0];
 	lut->clut_table   = &lut->table_data[in_chan*num_input_table_entries];
 	lut->output_table = &lut->table_data[in_chan*num_input_table_entries + clut_size*out_chan];
 	lut->num_input_table_entries  = num_input_table_entries;
 	lut->num_output_table_entries = num_output_table_entries;
 	lut->num_input_channels   = read_u8(src, offset + 8);
 	lut->num_output_channels  = read_u8(src, offset + 9);
 	lut->num_clut_grid_points = read_u8(src, offset + 10);
 	lut->e00 = read_s15Fixed16Number(src, offset+12);
 	lut->e01 = read_s15Fixed16Number(src, offset+16);
 	lut->e02 = read_s15Fixed16Number(src, offset+20);
 	lut->e10 = read_s15Fixed16Number(src, offset+24);
 	lut->e11 = read_s15Fixed16Number(src, offset+28);
 	lut->e12 = read_s15Fixed16Number(src, offset+32);
 	lut->e20 = read_s15Fixed16Number(src, offset+36);
 	lut->e21 = read_s15Fixed16Number(src, offset+40);
 	lut->e22 = read_s15Fixed16Number(src, offset+44);
 	for (i = 0; i < lut->num_input_table_entries * in_chan; i++) {
 		if (type == LUT8_TYPE) {
 			lut->input_table[i] = uInt8Number_to_float(read_uInt8Number(src, offset + 52 + i * entry_size));
 		} else {
 			lut->input_table[i] = uInt16Number_to_float(read_uInt16Number(src, offset + 52 + i * entry_size));
 		}
 	}
 	clut_offset = offset + 52 + lut->num_input_table_entries * in_chan * entry_size;
 	for (i = 0; i < clut_size * out_chan; i+=3) {
 		if (type == LUT8_TYPE) {
 			lut->clut_table[i+0] = uInt8Number_to_float(read_uInt8Number(src, clut_offset + i*entry_size + 0));
 			lut->clut_table[i+1] = uInt8Number_to_float(read_uInt8Number(src, clut_offset + i*entry_size + 1));
 			lut->clut_table[i+2] = uInt8Number_to_float(read_uInt8Number(src, clut_offset + i*entry_size + 2));
 		} else {
 			lut->clut_table[i+0] = uInt16Number_to_float(read_uInt16Number(src, clut_offset + i*entry_size + 0));
 			lut->clut_table[i+1] = uInt16Number_to_float(read_uInt16Number(src, clut_offset + i*entry_size + 2));
 			lut->clut_table[i+2] = uInt16Number_to_float(read_uInt16Number(src, clut_offset + i*entry_size + 4));
 		}
 	}
 	output_offset = clut_offset + clut_size * out_chan * entry_size;
 	for (i = 0; i < lut->num_output_table_entries * out_chan; i++) {
 		if (type == LUT8_TYPE) {
 			lut->output_table[i] = uInt8Number_to_float(read_uInt8Number(src, output_offset + i*entry_size));
 		} else {
 			lut->output_table[i] = uInt16Number_to_float(read_uInt16Number(src, output_offset + i*entry_size));
 		}
 	}
 	return lut;
 }
 static void read_rendering_intent(qcms_profile *profile, struct mem_source *src)
 {
 	profile->rendering_intent = read_u32(src, 64);
 	switch (profile->rendering_intent) {
 		case QCMS_INTENT_PERCEPTUAL:
 		case QCMS_INTENT_SATURATION:
 		case QCMS_INTENT_RELATIVE_COLORIMETRIC:
 		case QCMS_INTENT_ABSOLUTE_COLORIMETRIC:
 			break;
 		default:
 			invalid_source(src, "unknown rendering intent");
 	}
 }
 qcms_profile *qcms_profile_create(void)
 {
 	return calloc(sizeof(qcms_profile), 1);
 }
 /* build sRGB gamma table */
 /* based on cmsBuildParametricGamma() */
 static uint16_t *build_sRGB_gamma_table(int num_entries)
 {
 	int i;
 	/* taken from lcms: Build_sRGBGamma() */
 	double gamma = 2.4;
 	double a = 1./1.055;
 	double b = 0.055/1.055;
 	double c = 1./12.92;
 	double d = 0.04045;
 	uint16_t *table = malloc(sizeof(uint16_t) * num_entries);
 	if (!table)
 		return NULL;
 	for (i=0; i<num_entries; i++) {
 		double x = (double)i / (num_entries-1);
 		double y, output;
 		// IEC 61966-2.1 (sRGB)
 		// Y = (aX + b)^Gamma | X >= d
 		// Y = cX             | X < d
 		if (x >= d) {
 			double e = (a*x + b);
 			if (e > 0)
 				y = pow(e, gamma);
 			else
 				y = 0;
 		} else {
 			y = c*x;
 		}
 		// Saturate -- this could likely move to a separate function
 		output = y * 65535. + .5;
 		if (output > 65535.)
 			output = 65535;
 		if (output < 0)
 			output = 0;
 		table[i] = (uint16_t)floor(output);
 	}
 	return table;
 }
 static struct curveType *curve_from_table(uint16_t *table, int num_entries)
 {
 	struct curveType *curve;
 	int i;
 	curve = malloc(sizeof(struct curveType) + sizeof(uInt16Number)*num_entries);
 	if (!curve)
 		return NULL;
 	curve->type = CURVE_TYPE;
 	curve->count = num_entries;
 	for (i = 0; i < num_entries; i++) {
 		curve->data[i] = table[i];
 	}
 	return curve;
 }
 static uint16_t float_to_u8Fixed8Number(float a)
 {
 	if (a > (255.f + 255.f/256))
 		return 0xffff;
 	else if (a < 0.f)
 		return 0;
 	else
 		return floorf(a*256.f + .5f);
 }
 static struct curveType *curve_from_gamma(float gamma)
 {
 	struct curveType *curve;
 	int num_entries = 1;
 	curve = malloc(sizeof(struct curveType) + sizeof(uInt16Number)*num_entries);
 	if (!curve)
 		return NULL;
 	curve->count = num_entries;
 	curve->data[0] = float_to_u8Fixed8Number(gamma);
   	curve->type = CURVE_TYPE;
 	return curve;
 }
 //XXX: it would be nice if we had a way of ensuring
 // everything in a profile was initialized regardless of how it was created
 //XXX: should this also be taking a black_point?
 /* similar to CGColorSpaceCreateCalibratedRGB */
 qcms_profile* qcms_profile_create_rgb_with_gamma(
 		qcms_CIE_xyY white_point,
 		qcms_CIE_xyYTRIPLE primaries,
 		float gamma)
 {
 	qcms_profile* profile = qcms_profile_create();
 	if (!profile)
 		return NO_MEM_PROFILE;
 	//XXX: should store the whitepoint
 	if (!set_rgb_colorants(profile, white_point, primaries)) {
 		qcms_profile_release(profile);
 		return INVALID_PROFILE;
 	}
 	profile->redTRC = curve_from_gamma(gamma);
 	profile->blueTRC = curve_from_gamma(gamma);
 	profile->greenTRC = curve_from_gamma(gamma);
 	if (!profile->redTRC || !profile->blueTRC || !profile->greenTRC) {
 		qcms_profile_release(profile);
 		return NO_MEM_PROFILE;
 	}
 	profile->class = DISPLAY_DEVICE_PROFILE;
 	profile->rendering_intent = QCMS_INTENT_PERCEPTUAL;
 	profile->color_space = RGB_SIGNATURE;
 	return profile;
 }
 qcms_profile* qcms_profile_create_rgb_with_table(
 		qcms_CIE_xyY white_point,
 		qcms_CIE_xyYTRIPLE primaries,
 		uint16_t *table, int num_entries)
 {
 	qcms_profile* profile = qcms_profile_create();
 	if (!profile)
 		return NO_MEM_PROFILE;
 	//XXX: should store the whitepoint
 	if (!set_rgb_colorants(profile, white_point, primaries)) {
 		qcms_profile_release(profile);
 		return INVALID_PROFILE;
 	}
 	profile->redTRC = curve_from_table(table, num_entries);
 	profile->blueTRC = curve_from_table(table, num_entries);
 	profile->greenTRC = curve_from_table(table, num_entries);
 	if (!profile->redTRC || !profile->blueTRC || !profile->greenTRC) {
 		qcms_profile_release(profile);
 		return NO_MEM_PROFILE;
 	}
 	profile->class = DISPLAY_DEVICE_PROFILE;
 	profile->rendering_intent = QCMS_INTENT_PERCEPTUAL;
 	profile->color_space = RGB_SIGNATURE;
 	return profile;
 }
 /* from lcms: cmsWhitePointFromTemp */
 /* tempK must be >= 4000. and <= 25000.
  * Invalid values of tempK will return
  * (x,y,Y) = (-1.0, -1.0, -1.0)
  * similar to argyll: icx_DTEMP2XYZ() */
 static qcms_CIE_xyY white_point_from_temp(int temp_K)
 {
 	qcms_CIE_xyY white_point;
 	double x, y;
 	double T, T2, T3;
 	// double M1, M2;
 	// No optimization provided.
 	T = temp_K;
 	T2 = T*T;            // Square
 	T3 = T2*T;           // Cube
 	// For correlated color temperature (T) between 4000K and 7000K:
 	if (T >= 4000. && T <= 7000.) {
 		x = -4.6070*(1E9/T3) + 2.9678*(1E6/T2) + 0.09911*(1E3/T) + 0.244063;
 	} else {
 		// or for correlated color temperature (T) between 7000K and 25000K:
 		if (T > 7000.0 && T <= 25000.0) {
 			x = -2.0064*(1E9/T3) + 1.9018*(1E6/T2) + 0.24748*(1E3/T) + 0.237040;
 		} else {
 			// Invalid tempK
 			white_point.x = -1.0;
 			white_point.y = -1.0;
 			white_point.Y = -1.0;
 			assert(0 && "invalid temp");
 			return white_point;
 		}
 	}
 	// Obtain y(x)
 	y = -3.000*(x*x) + 2.870*x - 0.275;
 	// wave factors (not used, but here for futures extensions)
 	// M1 = (-1.3515 - 1.7703*x + 5.9114 *y)/(0.0241 + 0.2562*x - 0.7341*y);
 	// M2 = (0.0300 - 31.4424*x + 30.0717*y)/(0.0241 + 0.2562*x - 0.7341*y);
 	// Fill white_point struct
 	white_point.x = x;
 	white_point.y = y;
 	white_point.Y = 1.0;
 	return white_point;
 }
 qcms_profile* qcms_profile_sRGB(void)
 {
 	qcms_profile *profile;
 	uint16_t *table;
 	qcms_CIE_xyYTRIPLE Rec709Primaries = {
 		{0.6400, 0.3300, 1.0},
 		{0.3000, 0.6000, 1.0},
 		{0.1500, 0.0600, 1.0}
 	};
 	qcms_CIE_xyY D65;
 	D65 = white_point_from_temp(6504);
 	table = build_sRGB_gamma_table(1024);
 	if (!table)
 		return NO_MEM_PROFILE;
 	profile = qcms_profile_create_rgb_with_table(D65, Rec709Primaries, table, 1024);
 	free(table);
 	return profile;
 }
 /* qcms_profile_from_memory does not hold a reference to the memory passed in */
 qcms_profile* qcms_profile_from_memory(const void *mem, size_t size)
 {
 	uint32_t length;
 	struct mem_source source;
 	struct mem_source *src = &source;
 	struct tag_index index;
 	qcms_profile *profile;
 	source.buf = mem;
 	source.size = size;
 	source.valid = true;
 	if (size < 4)
 		return INVALID_PROFILE;
 	length = read_u32(src, 0);
 	if (length <= size) {
 		// shrink the area that we can read if appropriate
 		source.size = length;
 	} else {
 		return INVALID_PROFILE;
 	}
 	/* ensure that the profile size is sane so it's easier to reason about */
 	if (source.size <= 64 || source.size >= MAX_PROFILE_SIZE)
 		return INVALID_PROFILE;
 	profile = qcms_profile_create();
 	if (!profile)
 		return NO_MEM_PROFILE;
 	check_CMM_type_signature(src);
 	check_profile_version(src);
 	read_class_signature(profile, src);
 	read_rendering_intent(profile, src);
 	read_color_space(profile, src);
 	read_pcs(profile, src);
 	//TODO read rest of profile stuff
 	if (!src->valid)
 		goto invalid_profile;
 	index = read_tag_table(profile, src);
 	if (!src->valid || !index.tags)
 		goto invalid_tag_table;
 	if (find_tag(index, TAG_CHAD)) {
 		profile->chromaticAdaption = read_tag_s15Fixed16ArrayType(src, index, TAG_CHAD);
 	} else {
 		profile->chromaticAdaption.invalid = true; //Signal the data is not present
 	}
 	if (profile->class == DISPLAY_DEVICE_PROFILE || profile->class == INPUT_DEVICE_PROFILE ||
             profile->class == OUTPUT_DEVICE_PROFILE  || profile->class == COLOR_SPACE_PROFILE) {
 		if (profile->color_space == RGB_SIGNATURE) {
 			if (find_tag(index, TAG_A2B0)) {
 				if (read_u32(src, find_tag(index, TAG_A2B0)->offset) == LUT8_TYPE ||
 				    read_u32(src, find_tag(index, TAG_A2B0)->offset) == LUT16_TYPE) {
 					profile->A2B0 = read_tag_lutType(src, index, TAG_A2B0);
 				} else if (read_u32(src, find_tag(index, TAG_A2B0)->offset) == LUT_MAB_TYPE) {
 					profile->mAB = read_tag_lutmABType(src, index, TAG_A2B0);
 				}
 			}
 			if (find_tag(index, TAG_B2A0)) {
 				if (read_u32(src, find_tag(index, TAG_B2A0)->offset) == LUT8_TYPE ||
 				    read_u32(src, find_tag(index, TAG_B2A0)->offset) == LUT16_TYPE) {
 					profile->B2A0 = read_tag_lutType(src, index, TAG_B2A0);
 				} else if (read_u32(src, find_tag(index, TAG_B2A0)->offset) == LUT_MBA_TYPE) {
 					profile->mBA = read_tag_lutmABType(src, index, TAG_B2A0);
 				}
 			}
 			if (find_tag(index, TAG_rXYZ) || !qcms_supports_iccv4) {
 				profile->redColorant = read_tag_XYZType(src, index, TAG_rXYZ);
 				profile->greenColorant = read_tag_XYZType(src, index, TAG_gXYZ);
 				profile->blueColorant = read_tag_XYZType(src, index, TAG_bXYZ);
 			}
 			if (!src->valid)
 				goto invalid_tag_table;
 			if (find_tag(index, TAG_rTRC) || !qcms_supports_iccv4) {
 				profile->redTRC = read_tag_curveType(src, index, TAG_rTRC);
 				profile->greenTRC = read_tag_curveType(src, index, TAG_gTRC);
 				profile->blueTRC = read_tag_curveType(src, index, TAG_bTRC);
 				if (!profile->redTRC || !profile->blueTRC || !profile->greenTRC)
 					goto invalid_tag_table;
 			}
 		} else if (profile->color_space == GRAY_SIGNATURE) {
 			profile->grayTRC = read_tag_curveType(src, index, TAG_kTRC);
 			if (!profile->grayTRC)
 				goto invalid_tag_table;
 		} else {
 			assert(0 && "read_color_space protects against entering here");
 			goto invalid_tag_table;
 		}
 	} else {
 		goto invalid_tag_table;
 	}
 	if (!src->valid)
 		goto invalid_tag_table;
 	free(index.tags);
 	return profile;
 invalid_tag_table:
 	free(index.tags);
 invalid_profile:
 	qcms_profile_release(profile);
 	return INVALID_PROFILE;
 }
 qcms_intent qcms_profile_get_rendering_intent(qcms_profile *profile)
 {
 	return profile->rendering_intent;
 }
 icColorSpaceSignature
 qcms_profile_get_color_space(qcms_profile *profile)
 {
 	return profile->color_space;
 }
 static void lut_release(struct lutType *lut)
 {
 	free(lut);
 }
 void qcms_profile_release(qcms_profile *profile)
 {
 	if (profile->output_table_r)
 		precache_release(profile->output_table_r);
 	if (profile->output_table_g)
 		precache_release(profile->output_table_g);
 	if (profile->output_table_b)
 		precache_release(profile->output_table_b);
 	if (profile->A2B0)
 		lut_release(profile->A2B0);
 	if (profile->B2A0)
 		lut_release(profile->B2A0);
 	if (profile->mAB)
 		mAB_release(profile->mAB);
 	if (profile->mBA)
 		mAB_release(profile->mBA);
 	free(profile->redTRC);
 	free(profile->blueTRC);
 	free(profile->greenTRC);
 	free(profile->grayTRC);
 	free(profile);
 }
 #include <stdio.h>
 static void qcms_data_from_file(FILE *file, void **mem, size_t *size)
 {
 	uint32_t length, remaining_length;
 	size_t read_length;
 	be32 length_be;
 	void *data;
 	*mem = NULL;
 	*size = 0;
 	if (fread(&length_be, 1, sizeof(length_be), file) != sizeof(length_be))
 		return;
 	length = be32_to_cpu(length_be);
 	if (length > MAX_PROFILE_SIZE || length < sizeof(length_be))
 		return;
 	/* allocate room for the entire profile */
 	data = malloc(length);
 	if (!data)
 		return;
 	/* copy in length to the front so that the buffer will contain the entire profile */
 	*((be32*)data) = length_be;
 	remaining_length = length - sizeof(length_be);
 	/* read the rest profile */
 	read_length = fread((unsigned char*)data + sizeof(length_be), 1, remaining_length, file);
 	if (read_length != remaining_length) {
 		free(data);
 		return;
 	}
 	/* successfully get the profile.*/
 	*mem = data;
 	*size = length;
 }
 qcms_profile* qcms_profile_from_file(FILE *file)
 {
 	size_t length;
 	qcms_profile *profile;
 	void *data;
 	qcms_data_from_file(file, &data, &length);
 	if ((data == NULL) || (length == 0))
 		return INVALID_PROFILE;
 	profile = qcms_profile_from_memory(data, length);
 	free(data);
 	return profile;
 }
 qcms_profile* qcms_profile_from_path(const char *path)
 {
 	qcms_profile *profile = NULL;
 	FILE *file = fopen(path, "rb");
 	if (file) {
 		profile = qcms_profile_from_file(file);
 		fclose(file);
 	}
 	return profile;
 }
 void qcms_data_from_path(const char *path, void **mem, size_t *size)
 {
 	FILE *file = NULL;
 	*mem = NULL;
 	*size  = 0;
 	file = fopen(path, "rb");
 	if (file) {
 		qcms_data_from_file(file, mem, size);
 		fclose(file);
 	}
 }
 #ifdef _WIN32
 /* Unicode path version */
 qcms_profile* qcms_profile_from_unicode_path(const wchar_t *path)
 {
 	qcms_profile *profile = NULL;
 	FILE *file = _wfopen(path, L"rb");
 	if (file) {
 		profile = qcms_profile_from_file(file);
 		fclose(file);
 	}
 	return profile;
 }
 void qcms_data_from_unicode_path(const wchar_t *path, void **mem, size_t *size)
 {
 	FILE *file = NULL;
 	*mem = NULL;
 	*size  = 0;
 	file = _wfopen(path, L"rb");
 	if (file) {
 		qcms_data_from_file(file, mem, size);
 		fclose(file);
 	}
 }
 #endif
 /*
 * This function constructs an ICC profile memory with given header and tag data,
 * which can be read via qcms_profile_from_memory(). that means, we must satisfy
 * the profiler header type check (which seems not complete till now) and proper
 * information to read data from the tag table and tag data elements memory.
 *
 * To construct a valid ICC profile, its divided into three steps :
 *	(1) construct the r/g/bXYZ part
 *	(2) construct the r/g/bTRC part
 *	(3) construct the profile header
 * this is a hardcode step just for "create_rgb_with_gamma", it is the only
 * requirement till now, maybe we can make this method more general in future,
 *
 * NOTE : some of the parameters below are hardcode, please refer to the ICC documentation.
 */
 #define ICC_PROFILE_HEADER_LENGTH 128
 void qcms_data_create_rgb_with_gamma(qcms_CIE_xyY white_point, qcms_CIE_xyYTRIPLE primaries, float gamma, void **mem, size_t *size)
 {
 	uint32_t length, offset, index, xyz_count, trc_count;
 	size_t tag_table_offset, tag_data_offset;
 	void *data;
 	struct matrix colorants;
 	uint32_t TAG_XYZ[3] = {TAG_rXYZ, TAG_gXYZ, TAG_bXYZ};
 	uint32_t TAG_TRC[3] = {TAG_rTRC, TAG_gTRC, TAG_bTRC};
 	if ((mem == NULL) || (size == NULL))
 		return;
 	*mem = NULL;
 	*size = 0;
 	/*
 	* total length = icc profile header(128) + tag count(4) +
 	* (tag table item (12) * total tag (6 = 3 rTRC + 3 rXYZ)) + rTRC elements data (3 * 20)
 	* + rXYZ elements data (3*16), and all tag data elements must start at the 4-byte boundary.
 	*/
 	xyz_count = 3; // rXYZ, gXYZ, bXYZ
 	trc_count = 3; // rTRC, gTRC, bTRC
 	length =  ICC_PROFILE_HEADER_LENGTH + 4 + (12 * (xyz_count + trc_count)) + (xyz_count * 20) + (trc_count * 16);
 	// reserve the total memory.
 	data = malloc(length);
 	if (!data)
 		return;
 	memset(data, 0, length);
 	// Part1 : write rXYZ, gXYZ and bXYZ
 	if (!get_rgb_colorants(&colorants, white_point, primaries)) {
 		free(data);
 		return;
 	}
 	 // the position of first tag's signature in tag table
 	tag_table_offset = ICC_PROFILE_HEADER_LENGTH + 4;
 	tag_data_offset = ICC_PROFILE_HEADER_LENGTH + 4 +
 	   (12 * (xyz_count + trc_count)); // the start of tag data elements.
 	for (index = 0; index < xyz_count; ++index) {
 		// tag table
 		write_u32(data, tag_table_offset, TAG_XYZ[index]);
 		write_u32(data, tag_table_offset+4, tag_data_offset);
 		write_u32(data, tag_table_offset+8, 20); // 20 bytes per TAG_(r/g/b)XYZ tag element
 		// tag data element
 		write_u32(data, tag_data_offset, XYZ_TYPE);
 		// reserved 4 bytes.
 		write_u32(data, tag_data_offset+8, double_to_s15Fixed16Number(colorants.m[0][index]));
 		write_u32(data, tag_data_offset+12, double_to_s15Fixed16Number(colorants.m[1][index]));
 		write_u32(data, tag_data_offset+16, double_to_s15Fixed16Number(colorants.m[2][index]));
 		tag_table_offset += 12;
 		tag_data_offset += 20;
 	}
 	// Part2 : write rTRC, gTRC and bTRC
 	for (index = 0; index < trc_count; ++index) {
 		// tag table
 		write_u32(data, tag_table_offset, TAG_TRC[index]);
 		write_u32(data, tag_table_offset+4, tag_data_offset);
 		write_u32(data, tag_table_offset+8, 14); // 14 bytes per TAG_(r/g/b)TRC element
 		// tag data element
 		write_u32(data, tag_data_offset, CURVE_TYPE);
 		// reserved 4 bytes.
 		write_u32(data, tag_data_offset+8, 1); // count
 		write_u16(data, tag_data_offset+12, float_to_u8Fixed8Number(gamma));
 		tag_table_offset += 12;
 		tag_data_offset += 16;
 	}
 	/* Part3 : write profile header
 	 *
 	 * Important header fields are left empty. This generates a profile for internal use only.
 	 * We should be generating: Profile version (04300000h), Profile signature (acsp),
 	 * PCS illumiant field. Likewise mandatory profile tags are omitted.
 	 */
 	write_u32(data, 0, length); // the total length of this memory
 	write_u32(data, 12, DISPLAY_DEVICE_PROFILE); // profile->class
 	write_u32(data, 16, RGB_SIGNATURE); // profile->color_space
 	write_u32(data, 20, XYZ_SIGNATURE); // profile->pcs
 	write_u32(data, 64, QCMS_INTENT_PERCEPTUAL); // profile->rendering_intent
 	write_u32(data, ICC_PROFILE_HEADER_LENGTH, 6); // total tag count
 	// prepare the result
 	*mem = data;
 	*size = length;
 }

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gfx/qcms/iccread.c@97036ab72558 (annotated)

gfx/qcms/iccread.c