jdatasrc.c File Reference

#include "jinclude.h"
#include "jpeglib.h"
#include "jerror.h"

Include dependency graph for jdatasrc.c:

Go to the source code of this file.

Classes
struct	my_source_mgr

Macros
#define	INPUT_BUF_SIZE   4096 /* choose an efficiently fread'able size */

Typedefs
typedef my_source_mgr *	my_src_ptr

Functions
	init_source (j_decompress_ptr cinfo)
	init_mem_source (j_decompress_ptr cinfo)
	fill_input_buffer (j_decompress_ptr cinfo)
	fill_mem_input_buffer (j_decompress_ptr cinfo)
	skip_input_data (j_decompress_ptr cinfo, long num_bytes)
	term_source (j_decompress_ptr cinfo)
	jpeg_stdio_src (j_decompress_ptr cinfo, FILE *infile)
	jpeg_mem_src (j_decompress_ptr cinfo, const unsigned char *inbuffer, unsigned long insize)

Macro Definition Documentation

INPUT_BUF_SIZE

#define INPUT_BUF_SIZE   4096 /* choose an efficiently fread'able size */

Definition at line 36 of file jdatasrc.c.

Typedef Documentation

my_src_ptr

typedef my_source_mgr* my_src_ptr

Definition at line 34 of file jdatasrc.c.

Function Documentation

fill_input_buffer()

fill_input_buffer

(

j_decompress_ptr

cinfo

)

Definition at line 97 of file jdatasrc.c.

{
  my_src_ptr src = (my_src_ptr) cinfo->src;
  size_t nbytes;

  nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);

  if (nbytes <= 0) {
    if (src->start_of_file) /* Treat empty input file as fatal error */
      ERREXIT(cinfo, JERR_INPUT_EMPTY);
    WARNMS(cinfo, JWRN_JPEG_EOF);
    /* Insert a fake EOI marker */
    src->buffer[0] = (JOCTET) 0xFF;
    src->buffer[1] = (JOCTET) JPEG_EOI;
    nbytes = 2;
  }

  src->pub.next_input_byte = src->buffer;
  src->pub.bytes_in_buffer = nbytes;
  src->start_of_file = FALSE;

  return TRUE;
}

Referenced by jpeg_stdio_src().

fill_mem_input_buffer()

fill_mem_input_buffer

(

j_decompress_ptr

cinfo

)

Definition at line 122 of file jdatasrc.c.

{
  static const JOCTET mybuffer[4] = {
    (JOCTET) 0xFF, (JOCTET) JPEG_EOI, 0, 0
  };

  /* The whole JPEG data is expected to reside in the supplied memory
   * buffer, so any request for more data beyond the given buffer size
   * is treated as an error.
   */
  WARNMS(cinfo, JWRN_JPEG_EOF);

  /* Insert a fake EOI marker */

  cinfo->src->next_input_byte = mybuffer;
  cinfo->src->bytes_in_buffer = 2;

  return TRUE;
}

Referenced by jpeg_mem_src().

init_mem_source()

init_mem_source

(

j_decompress_ptr

cinfo

)

Definition at line 57 of file jdatasrc.c.

{
  /* no work necessary here */
}

Referenced by jpeg_mem_src().

init_source()

init_source

(

j_decompress_ptr

cinfo

)

Definition at line 45 of file jdatasrc.c.

{
  my_src_ptr src = (my_src_ptr) cinfo->src;

  /* We reset the empty-input-file flag for each image,
   * but we don't clear the input buffer.
   * This is correct behavior for reading a series of images from one source.
   */
  src->start_of_file = TRUE;
}

Referenced by jpeg_stdio_src().

jpeg_mem_src()

jpeg_mem_src	(	j_decompress_ptr	cinfo,
		const unsigned char *	inbuffer,
		unsigned long	insize
	)

Definition at line 249 of file jdatasrc.c.

{
  struct jpeg_source_mgr * src;

  if (inbuffer == NULL || insize == 0)  /* Treat empty input as fatal error */
    ERREXIT(cinfo, JERR_INPUT_EMPTY);

  /* The source object is made permanent so that a series of JPEG images
   * can be read from the same buffer by calling jpeg_mem_src only before
   * the first one.
   */
  if (cinfo->src == NULL) { /* first time for this JPEG object? */
    cinfo->src = (struct jpeg_source_mgr *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                  SIZEOF(struct jpeg_source_mgr));
  }

  src = cinfo->src;
  src->init_source = init_mem_source;
  src->fill_input_buffer = fill_mem_input_buffer;
  src->skip_input_data = skip_input_data;
  src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
  src->term_source = term_source;
  src->bytes_in_buffer = (size_t) insize;
  src->next_input_byte = (const JOCTET *) inbuffer;
}

jpeg_stdio_src()

jpeg_stdio_src	(	j_decompress_ptr	cinfo,
		FILE *	infile
	)

Definition at line 210 of file jdatasrc.c.

{
  my_src_ptr src;

  /* The source object and input buffer are made permanent so that a series
   * of JPEG images can be read from the same file by calling jpeg_stdio_src
   * only before the first one.  (If we discarded the buffer at the end of
   * one image, we'd likely lose the start of the next one.)
   * This makes it unsafe to use this manager and a different source
   * manager serially with the same JPEG object.  Caveat programmer.
   */
  if (cinfo->src == NULL) { /* first time for this JPEG object? */
    cinfo->src = (struct jpeg_source_mgr *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                  SIZEOF(my_source_mgr));
    src = (my_src_ptr) cinfo->src;
    src->buffer = (JOCTET *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                  INPUT_BUF_SIZE * SIZEOF(JOCTET));
  }

  src = (my_src_ptr) cinfo->src;
  src->pub.init_source = init_source;
  src->pub.fill_input_buffer = fill_input_buffer;
  src->pub.skip_input_data = skip_input_data;
  src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
  src->pub.term_source = term_source;
  src->infile = infile;
  src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
  src->pub.next_input_byte = NULL; /* until buffer loaded */
}

Referenced by main(), and read_JPEG_file().

skip_input_data()

skip_input_data	(	j_decompress_ptr	cinfo,
		long	num_bytes
	)

Definition at line 156 of file jdatasrc.c.

{
  struct jpeg_source_mgr * src = cinfo->src;

  /* Just a dumb implementation for now.  Could use fseek() except
   * it doesn't work on pipes.  Not clear that being smart is worth
   * any trouble anyway --- large skips are infrequent.
   */
  if (num_bytes > 0) {
    while (num_bytes > (long) src->bytes_in_buffer) {
      num_bytes -= (long) src->bytes_in_buffer;
      (void) (*src->fill_input_buffer) (cinfo);
      /* note we assume that fill_input_buffer will never return FALSE,
       * so suspension need not be handled.
       */
    }
    src->next_input_byte += (size_t) num_bytes;
    src->bytes_in_buffer -= (size_t) num_bytes;
  }
}

Referenced by jpeg_mem_src(), and jpeg_stdio_src().

term_source()

term_source

(

j_decompress_ptr

cinfo

)

Definition at line 197 of file jdatasrc.c.

{
  /* no work necessary here */
}

Referenced by jpeg_mem_src(), and jpeg_stdio_src().