Initial KTX file decoder

src/utils/SkKTXFile.cpp

+
+/*
+ * 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 "SkEndian.h"
+
+#include "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
+};
+

[robertphillips, 2014/06/03 15:28:02]

// magic code used by the KTX format to check for endianess ?
kKTX_... ?

[krajcevski, 2014/06/03 15:41:46]

Done.

+static const uint32_t KTX_ENDIANNESS_CODE = 0x04030201;
+
+bool SkKTXFile::KeyValue::readKeyAndValue(const uint8_t* data) {
+    const char *key = reinterpret_cast<const char *>(data);
+    const char *value = key;
+

[robertphillips, 2014/06/03 15:28:02]

Much clearer.

+    size_t bytesRead = 0;
+    while (*value != '\0' && bytesRead < this->fDataSz) {
+        ++bytesRead;
+        ++value;
+    }
+
+    // Error of some sort..
+    if (bytesRead >= this->fDataSz) {
+        return false;
+    }
+
+    // Read the zero terminator
+    ++bytesRead;
+    ++value;
+
+    size_t bytesLeft = this->fDataSz - bytesRead;
+    this->fKey.set(key, bytesRead);
+    if (bytesLeft > 0) {
+        this->fValue.set(value, bytesLeft);
+    } else {
+        return false;
+    }
+
+    return true;
+}
+
+uint32_t SkKTXFile::readInt(const uint8_t** buf, size_t* bytesLeft) const {
+    SkASSERT(NULL != buf && NULL != bytesLeft);
+
+    uint32_t result;
+

[robertphillips, 2014/06/03 15:28:02]

"if (" -- add space ?

[krajcevski, 2014/06/03 15:41:46]

Done.

+    if(*bytesLeft < 4) {
+        SkASSERT(false);
+        return 0;
+    }
+
+    memcpy(&result, *buf, 4);
+    *buf += 4;
+
+    if (fSwapBytes) {
+        SkEndianSwap32(result);
+    }
+
+    *bytesLeft -= 4;
+
+    return result;
+}
+
+bool SkKTXFile::isETC1() const {
+    return this->valid() && GR_GL_COMPRESSED_RGB8_ETC1 == fHeader.fGLInternalFormat;
+}
+
+bool SkKTXFile::isRGBA8() const {
+    return this->valid() && GR_GL_RGBA8 == fHeader.fGLInternalFormat;
+}
+
+bool SkKTXFile::isRGB8() const {
+    return this->valid() && GR_GL_RGB8 == fHeader.fGLInternalFormat;
+}
+
+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 endianness = this->readInt(&buf, &bytesLeft);
+    fSwapBytes = KTX_ENDIANNESS_CODE != endianness;
+
+    // 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. If the internal format is
+        // compressed, the the GLType field in the header must be zero.
+        // 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;
+        }
+    }
+
+    // Make sure that we have enough bytes left for the key/value
+    // data according to what was said in the header.
+    if (bytesLeft < fHeader.fBytesOfKeyValueData) {
+        return false;
+    }
+
+    // Next read the key value pairs
+    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.push_back(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);
+
+    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);
+
+        // Truncated file.
+        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) {
+                    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);
+}