diff -r 000000000000 -r 6474c204b198 js/src/vm/Compression.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/vm/Compression.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,131 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "vm/Compression.h"
+
+#include "js/Utility.h"
+
+using namespace js;
+
+#if USE_ZLIB
+static void *
+zlib_alloc(void *cx, uInt items, uInt size)
+{
+    return js_calloc(items, size);
+}
+
+static void
+zlib_free(void *cx, void *addr)
+{
+    js_free(addr);
+}
+
+Compressor::Compressor(const unsigned char *inp, size_t inplen)
+    : inp(inp),
+      inplen(inplen),
+      outbytes(0),
+      initialized(false)
+{
+    JS_ASSERT(inplen > 0);
+    zs.opaque = nullptr;
+    zs.next_in = (Bytef *)inp;
+    zs.avail_in = 0;
+    zs.next_out = nullptr;
+    zs.avail_out = 0;
+    zs.zalloc = zlib_alloc;
+    zs.zfree = zlib_free;
+}
+
+
+Compressor::~Compressor()
+{
+    if (initialized) {
+        int ret = deflateEnd(&zs);
+        if (ret != Z_OK) {
+            // If we finished early, we can get a Z_DATA_ERROR.
+            JS_ASSERT(ret == Z_DATA_ERROR);
+            JS_ASSERT(uInt(zs.next_in - inp) < inplen || !zs.avail_out);
+        }
+    }
+}
+
+bool
+Compressor::init()
+{
+    if (inplen >= UINT32_MAX)
+        return false;
+    // zlib is slow and we'd rather be done compression sooner
+    // even if it means decompression is slower which penalizes
+    // Function.toString()
+    int ret = deflateInit(&zs, Z_BEST_SPEED);
+    if (ret != Z_OK) {
+        JS_ASSERT(ret == Z_MEM_ERROR);
+        return false;
+    }
+    initialized = true;
+    return true;
+}
+
+void
+Compressor::setOutput(unsigned char *out, size_t outlen)
+{
+    JS_ASSERT(outlen > outbytes);
+    zs.next_out = out + outbytes;
+    zs.avail_out = outlen - outbytes;
+}
+
+Compressor::Status
+Compressor::compressMore()
+{
+    JS_ASSERT(zs.next_out);
+    uInt left = inplen - (zs.next_in - inp);
+    bool done = left <= CHUNKSIZE;
+    if (done)
+        zs.avail_in = left;
+    else if (zs.avail_in == 0)
+        zs.avail_in = CHUNKSIZE;
+    Bytef *oldout = zs.next_out;
+    int ret = deflate(&zs, done ? Z_FINISH : Z_NO_FLUSH);
+    outbytes += zs.next_out - oldout;
+    if (ret == Z_MEM_ERROR) {
+        zs.avail_out = 0;
+        return OOM;
+    }
+    if (ret == Z_BUF_ERROR || (done && ret == Z_OK)) {
+        JS_ASSERT(zs.avail_out == 0);
+        return MOREOUTPUT;
+    }
+    JS_ASSERT_IF(!done, ret == Z_OK);
+    JS_ASSERT_IF(done, ret == Z_STREAM_END);
+    return done ? DONE : CONTINUE;
+}
+
+bool
+js::DecompressString(const unsigned char *inp, size_t inplen, unsigned char *out, size_t outlen)
+{
+    JS_ASSERT(inplen <= UINT32_MAX);
+    z_stream zs;
+    zs.zalloc = zlib_alloc;
+    zs.zfree = zlib_free;
+    zs.opaque = nullptr;
+    zs.next_in = (Bytef *)inp;
+    zs.avail_in = inplen;
+    zs.next_out = out;
+    JS_ASSERT(outlen);
+    zs.avail_out = outlen;
+    int ret = inflateInit(&zs);
+    if (ret != Z_OK) {
+        JS_ASSERT(ret == Z_MEM_ERROR);
+        return false;
+    }
+    ret = inflate(&zs, Z_FINISH);
+    JS_ASSERT(ret == Z_STREAM_END);
+    ret = inflateEnd(&zs);
+    JS_ASSERT(ret == Z_OK);
+    return true;
+}
+#endif /* USE_ZLIB */
+