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      1 /*
      2  * Copyright 2015 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkJpegUtility.h"
      9 
     10 #include "SkCodecPriv.h"
     11 
     12 /*
     13  * Initialize the source manager
     14  */
     15 static void sk_init_source(j_decompress_ptr dinfo) {
     16     skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
     17     src->next_input_byte = (const JOCTET*) src->fBuffer;
     18     src->bytes_in_buffer = 0;
     19 }
     20 
     21 /*
     22  * Fill the input buffer from the stream
     23  */
     24 static boolean sk_fill_input_buffer(j_decompress_ptr dinfo) {
     25     skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
     26     size_t bytes = src->fStream->read(src->fBuffer, skjpeg_source_mgr::kBufferSize);
     27 
     28     // libjpeg is still happy with a less than full read, as long as the result is non-zero
     29     if (bytes == 0) {
     30         return false;
     31     }
     32 
     33     src->next_input_byte = (const JOCTET*) src->fBuffer;
     34     src->bytes_in_buffer = bytes;
     35     return true;
     36 }
     37 
     38 /*
     39  * Skip a certain number of bytes in the stream
     40  */
     41 static void sk_skip_input_data(j_decompress_ptr dinfo, long numBytes) {
     42     skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
     43     size_t bytes = (size_t) numBytes;
     44 
     45     if (bytes > src->bytes_in_buffer) {
     46         size_t bytesToSkip = bytes - src->bytes_in_buffer;
     47         if (bytesToSkip != src->fStream->skip(bytesToSkip)) {
     48             SkCodecPrintf("Failure to skip.\n");
     49             dinfo->err->error_exit((j_common_ptr) dinfo);
     50             return;
     51         }
     52 
     53         src->next_input_byte = (const JOCTET*) src->fBuffer;
     54         src->bytes_in_buffer = 0;
     55     } else {
     56         src->next_input_byte += numBytes;
     57         src->bytes_in_buffer -= numBytes;
     58     }
     59 }
     60 
     61 /*
     62  * We do not need to do anything to terminate our stream
     63  */
     64 static void sk_term_source(j_decompress_ptr dinfo)
     65 {
     66     // The current implementation of SkJpegCodec does not call
     67     // jpeg_finish_decompress(), so this function is never called.
     68     // If we want to modify this function to do something, we also
     69     // need to modify SkJpegCodec to call jpeg_finish_decompress().
     70 }
     71 
     72 /*
     73  * Constructor for the source manager that we provide to libjpeg
     74  * We provide skia implementations of all of the stream processing functions required by libjpeg
     75  */
     76 skjpeg_source_mgr::skjpeg_source_mgr(SkStream* stream)
     77     : fStream(stream)
     78 {
     79     init_source = sk_init_source;
     80     fill_input_buffer = sk_fill_input_buffer;
     81     skip_input_data = sk_skip_input_data;
     82     resync_to_restart = jpeg_resync_to_restart;
     83     term_source = sk_term_source;
     84 }
     85 
     86 /*
     87  * Call longjmp to continue execution on an error
     88  */
     89 void skjpeg_err_exit(j_common_ptr dinfo) {
     90     // Simply return to Skia client code
     91     // JpegDecoderMgr will take care of freeing memory
     92     skjpeg_error_mgr* error = (skjpeg_error_mgr*) dinfo->err;
     93     (*error->output_message) (dinfo);
     94     longjmp(error->fJmpBuf, 1);
     95 }
     96