src/codec/SkCodecPriv.h

/*
 * Copyright 2015 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkCodecPriv_DEFINED
#define SkCodecPriv_DEFINED

#include "SkImageInfo.h"
#include "SkSwizzler.h"
#include "SkTypes.h"

/*
 *
 * Helper routine for alpha result codes
 *
 */
#define INIT_RESULT_ALPHA                       \
    uint8_t zeroAlpha = 0;                      \
    uint8_t maxAlpha = 0xFF;

#define UPDATE_RESULT_ALPHA(alpha)              \
    zeroAlpha |= (alpha);                       \
    maxAlpha  &= (alpha);

#define COMPUTE_RESULT_ALPHA                    \
    SkSwizzler::GetResult(zeroAlpha, maxAlpha);

/*
 *
 * Compute row bytes for an image using pixels per byte
 *
 */
static inline size_t compute_row_bytes_ppb(int width, uint32_t pixelsPerByte) {
    return (width + pixelsPerByte - 1) / pixelsPerByte;
}

/*
 *
 * Compute row bytes for an image using bytes per pixel
 *
 */
static inline size_t compute_row_bytes_bpp(int width, uint32_t bytesPerPixel) {
    return width * bytesPerPixel;
}

/*
 *
 * Compute row bytes for an image
 *
 */
static inline size_t compute_row_bytes(int width, uint32_t bitsPerPixel) {
    if (bitsPerPixel < 16) {
        SkASSERT(0 == 8 % bitsPerPixel);
        const uint32_t pixelsPerByte = 8 / bitsPerPixel;
        return compute_row_bytes_ppb(width, pixelsPerByte);
    } else {
        SkASSERT(0 == bitsPerPixel % 8);
        const uint32_t bytesPerPixel = bitsPerPixel / 8;
        return compute_row_bytes_bpp(width, bytesPerPixel);
    }
}

/*
 *
 * Get a byte from a buffer
 * This method is unsafe, the caller is responsible for performing a check
 *
 */
static inline uint8_t get_byte(uint8_t* buffer, uint32_t i) {
    return buffer[i];
}

/*
 *
 * Get a short from a buffer
 * This method is unsafe, the caller is responsible for performing a check
 *
 */
static inline uint16_t get_short(uint8_t* buffer, uint32_t i) {
    uint16_t result;
    memcpy(&result, &(buffer[i]), 2);
#ifdef SK_CPU_BENDIAN
    return SkEndianSwap16(result);
#else
    return result;
#endif
}

/*
 *
 * Get an int from a buffer
 * This method is unsafe, the caller is responsible for performing a check
 *
 */
static inline uint32_t get_int(uint8_t* buffer, uint32_t i) {
    uint32_t result;
    memcpy(&result, &(buffer[i]), 4);
#ifdef SK_CPU_BENDIAN
    return SkEndianSwap32(result);
#else
    return result;
#endif
}

#endif // SkCodecPriv_DEFINED