Initial KTX file decoder

src/utils/SkKTXFile.cpp

Index: src/utils/SkKTXFile.cpp
diff --git a/src/utils/SkKTXFile.cpp b/src/utils/SkKTXFile.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..ceba49d73fa0fb306cc08e6022025c42e4c81e0c
--- /dev/null
+++ b/src/utils/SkKTXFile.cpp
@@ -0,0 +1,244 @@
+
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkKTXFile.h"
+#include "SkStream.h"
+
+#include "../gpu/gl/GrGLDefines.h"
+
+#define KTX_FILE_IDENTIFIER_SIZE 12
+static const uint8_t KTX_FILE_IDENTIFIER[KTX_FILE_IDENTIFIER_SIZE] = {
+    0xAB, 0x4B, 0x54, 0x58, 0x20, 0x31, 0x31, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A
+};
+
+static void swap_uint32(uint32_t& v) {
+    uint8_t *ptr = reinterpret_cast<uint8_t *>(&v);
+
+    uint8_t t;
+    t = ptr[0];
+    ptr[0] = ptr[3];
+    ptr[3] = t;
+
+    t = ptr[1];
+    ptr[1] = ptr[2];
+    ptr[2] = t;
+}
+
+bool SkKTXFile::KeyValue::readKeyAndValue(const uint8_t* data) {
+    const char *key = reinterpret_cast<const char *>(data);
+    const char *value = key;
+
+    size_t bytesRead = 0;
+    while (bytesRead < this->fDataSz) {
+        ++bytesRead;
+        if (*value == '\0') {
+            break;
+        }
+        ++value;
+    }
+
+    // Error of some sort..
+    if (bytesRead > 0 || bytesRead == this->fDataSz) {
+        return false;
+    }
+
+    fKey.set(key, bytesRead);
+    if (this->fDataSz > bytesRead) {
+        fValue.set(value, this->fDataSz - bytesRead);
+    } else {
+        return false;
+    }
+
+    return true;
+}
+
+uint32_t SkKTXFile::readInt(const uint8_t*& buf, size_t &bytesLeft) const {
+    uint32_t result;
+
+    if(bytesLeft < 4) {
+        SkASSERT(false);
+        return 0;
+    }
+
+    memcpy(&result, buf, 4);
+    buf += 4;
+
+    if (fSwapBytes) {
+        swap_uint32(result);
+    }
+
+    bytesLeft -= 4;
+
+    return result;
+}
+
+bool SkKTXFile::isETC1() const {
+    return valid() && fHeader.fGLInternalFormat == GR_GL_COMPRESSED_RGB8_ETC1;
+}
+
+bool SkKTXFile::isRGBA8() const {
+    return valid() && fHeader.fGLInternalFormat == GR_GL_RGBA8;
+}
+
+bool SkKTXFile::isRGB8() const {
+    return valid() && fHeader.fGLInternalFormat == GR_GL_RGB8;
+}
+
+bool SkKTXFile::readKTXFile(const uint8_t* data, size_t dataLen) {
+    const uint8_t *buf = data;
+    size_t bytesLeft = dataLen;
+
+    // Make sure original KTX header is there... this should have been checked
+    // already by a call to is_ktx()
+    SkASSERT(bytesLeft > KTX_FILE_IDENTIFIER_SIZE);
+    SkASSERT(0 == memcmp(KTX_FILE_IDENTIFIER, buf, KTX_FILE_IDENTIFIER_SIZE));
+    buf += KTX_FILE_IDENTIFIER_SIZE;
+    bytesLeft -= KTX_FILE_IDENTIFIER_SIZE;
+
+    // Read header, but first make sure that we have the proper space: we need
+    // two 32-bit ints: 1 for endianness, and another for the mandatory image
+    // size after the header.
+    if (bytesLeft < 8 + sizeof(Header)) {
+        return false;
+    }
+
+    uint32_t magic = this->readInt(buf, bytesLeft);
+    fSwapBytes = 0x04030201 != magic;
+
+    // Read header values
+    fHeader.fGLType                = this->readInt(buf, bytesLeft);
+    fHeader.fGLTypeSize            = this->readInt(buf, bytesLeft);
+    fHeader.fGLFormat              = this->readInt(buf, bytesLeft);
+    fHeader.fGLInternalFormat      = this->readInt(buf, bytesLeft);
+    fHeader.fGLBaseInternalFormat  = this->readInt(buf, bytesLeft);
+    fHeader.fPixelWidth            = this->readInt(buf, bytesLeft);
+    fHeader.fPixelHeight           = this->readInt(buf, bytesLeft);
+    fHeader.fPixelDepth            = this->readInt(buf, bytesLeft);
+    fHeader.fNumberOfArrayElements = this->readInt(buf, bytesLeft);
+    fHeader.fNumberOfFaces         = this->readInt(buf, bytesLeft);
+    fHeader.fNumberOfMipmapLevels  = this->readInt(buf, bytesLeft);
+    fHeader.fBytesOfKeyValueData   = this->readInt(buf, bytesLeft);
+
+    // Check for things that we understand...
+    {
+        // First, we only support compressed formats and single byte
+        // representations at the moment. In the future, we may support
+        // additional data types (such as GL_UNSIGNED_SHORT_5_6_5)
+        if (fHeader.fGLType != 0 && fHeader.fGLType != GR_GL_UNSIGNED_BYTE) {
+            return false;
+        }
+
+        // This means that for well-formatted KTX files, the glTypeSize
+        // field must be one...
+        if (fHeader.fGLTypeSize != 1) {
+            return false;
+        }
+
+        // We don't support 3D textures.
+        if (fHeader.fPixelDepth > 1) {
+            return false;
+        }
+
+        // We don't support texture arrays
+        if (fHeader.fNumberOfArrayElements > 1) {
+            return false;
+        }
+
+        // We don't support cube maps
+        if (fHeader.fNumberOfFaces > 1) {
+            return false;
+        }
+    }
+
+    // Next read the key value pairs
+    if (bytesLeft < fHeader.fBytesOfKeyValueData) {
+        return false;
+    }
+
+    size_t keyValueBytesRead = 0;
+    while (keyValueBytesRead < fHeader.fBytesOfKeyValueData) {
+        uint32_t keyValueBytes = this->readInt(buf, bytesLeft);
+        keyValueBytesRead = 4;
+
+        if (keyValueBytes > bytesLeft) {
+            return false;
+        }
+
+        KeyValue kv(keyValueBytes);
+        if (!kv.readKeyAndValue(buf)) {
+            return false;
+        }
+
+        fKeyValuePairs.append(1, &kv);
+
+        uint32_t keyValueBytesPadded = (keyValueBytes + 3) & ~3;
+        buf += keyValueBytesPadded;
+        keyValueBytesRead += keyValueBytesPadded;
+        bytesLeft -= keyValueBytesPadded;
+    }
+
+    // Read the pixel data...
+    int mipmaps = SkMax32(fHeader.fNumberOfMipmapLevels, 1);
+    SkASSERT(mipmaps == 1);
+
+    int arrayElements = SkMax32(fHeader.fNumberOfArrayElements, 1);
+    SkASSERT(arrayElements == 1);
+
+    int faces = SkMax32(fHeader.fNumberOfFaces, 1);
+    SkASSERT(faces == 1);
+
+    int depth = SkMax32(fHeader.fPixelDepth, 1);
+    SkASSERT(depth == 1);
+
+    int height = SkMax32(fHeader.fPixelHeight, 1);
+
+    for (int mipmap = 0; mipmap < mipmaps; ++mipmap) {
+        // Make sure that we have at least 4 more bytes for the first image size
+        if (bytesLeft < 4) {
+            return false;
+        }
+
+        uint32_t imgSize = this->readInt(buf, bytesLeft);
+
+        if (bytesLeft < imgSize) {
+            return false;
+        }
+
+        // !FIXME! If support is ever added for cube maps then the padding
+        // needs to be taken into account here.
+        for (int arrayElement = 0; arrayElement < arrayElements; ++arrayElement)
+        for (int face = 0; face < faces; ++face)
+        for (int z = 0; z < depth; ++z)
+        for (int y = 0; y < height; ++y) {
+            PixelData pd (buf, imgSize);
+            fPixelData.append(1, &pd);
+        }
+        
+        uint32_t imgSizePadded = (imgSize + 3) & ~3;
+        buf += imgSizePadded;
+        bytesLeft -= imgSizePadded;
+    }
+
+    return bytesLeft == 0;
+}
+
+bool SkKTXFile::is_ktx(const uint8_t *data) {
+    return 0 == memcmp(KTX_FILE_IDENTIFIER, data, KTX_FILE_IDENTIFIER_SIZE);
+}
+
+bool SkKTXFile::is_ktx(SkStreamRewindable* stream) {
+    // Read the KTX header and make sure it's valid.
+    unsigned char buf[KTX_FILE_IDENTIFIER_SIZE];
+    bool largeEnough =
+        stream->read((void*)buf, KTX_FILE_IDENTIFIER_SIZE) == KTX_FILE_IDENTIFIER_SIZE;
+    stream->rewind();
+    if (!largeEnough) {
+        return false;
+    }
+    return is_ktx(buf);
+}