--- /dev/null
+/*\r
+ * jmemsrc.c\r
+ *\r
+ * Copyright (C) 1994-1996, Thomas G. Lane.\r
+ * This file is part of the Independent JPEG Group's software.\r
+ * For conditions of distribution and use, see the accompanying README file.\r
+ *\r
+ * This file contains decompression data source routines for the case of\r
+ * reading JPEG data from a memory buffer that is preloaded with the entire\r
+ * JPEG file. This would not seem especially useful at first sight, but\r
+ * a number of people have asked for it.\r
+ * This is really just a stripped-down version of jdatasrc.c. Comparison\r
+ * of this code with jdatasrc.c may be helpful in seeing how to make\r
+ * custom source managers for other purposes.\r
+ */\r
+\r
+/* this is not a core library module, so it doesn't define JPEG_INTERNALS */\r
+#include "jinclude.h"\r
+#include "jpeglib.h"\r
+#include "jerror.h"\r
+\r
+\r
+/* Expanded data source object for memory input */\r
+\r
+typedef struct {\r
+ struct jpeg_source_mgr pub; /* public fields */\r
+\r
+ JOCTET eoi_buffer[2]; /* a place to put a dummy EOI */\r
+} my_source_mgr;\r
+\r
+typedef my_source_mgr * my_src_ptr;\r
+\r
+\r
+/*\r
+ * Initialize source --- called by jpeg_read_header\r
+ * before any data is actually read.\r
+ */\r
+\r
+METHODDEF(void)\r
+init_source (j_decompress_ptr cinfo)\r
+{\r
+ /* No work, since jpeg_memory_src set up the buffer pointer and count.\r
+ * Indeed, if we want to read multiple JPEG images from one buffer,\r
+ * this *must* not do anything to the pointer.\r
+ */\r
+}\r
+\r
+\r
+/*\r
+ * Fill the input buffer --- called whenever buffer is emptied.\r
+ *\r
+ * In this application, this routine should never be called; if it is called,\r
+ * the decompressor has overrun the end of the input buffer, implying we\r
+ * supplied an incomplete or corrupt JPEG datastream. A simple error exit\r
+ * might be the most appropriate response.\r
+ *\r
+ * But what we choose to do in this code is to supply dummy EOI markers\r
+ * in order to force the decompressor to finish processing and supply\r
+ * some sort of output image, no matter how corrupted.\r
+ */\r
+\r
+METHODDEF(boolean)\r
+fill_input_buffer (j_decompress_ptr cinfo)\r
+{\r
+ my_src_ptr src = (my_src_ptr) cinfo->src;\r
+\r
+ WARNMS(cinfo, JWRN_JPEG_EOF);\r
+\r
+ /* Create a fake EOI marker */\r
+ src->eoi_buffer[0] = (JOCTET) 0xFF;\r
+ src->eoi_buffer[1] = (JOCTET) JPEG_EOI;\r
+ src->pub.next_input_byte = src->eoi_buffer;\r
+ src->pub.bytes_in_buffer = 2;\r
+\r
+ return TRUE;\r
+}\r
+\r
+\r
+/*\r
+ * Skip data --- used to skip over a potentially large amount of\r
+ * uninteresting data (such as an APPn marker).\r
+ *\r
+ * If we overrun the end of the buffer, we let fill_input_buffer deal with\r
+ * it. An extremely large skip could cause some time-wasting here, but\r
+ * it really isn't supposed to happen ... and the decompressor will never\r
+ * skip more than 64K anyway.\r
+ */\r
+\r
+METHODDEF(void)\r
+skip_input_data (j_decompress_ptr cinfo, long num_bytes)\r
+{\r
+ my_src_ptr src = (my_src_ptr) cinfo->src;\r
+\r
+ if (num_bytes > 0) {\r
+ while (num_bytes > (long) src->pub.bytes_in_buffer) {\r
+ num_bytes -= (long) src->pub.bytes_in_buffer;\r
+ (void) fill_input_buffer(cinfo);\r
+ /* note we assume that fill_input_buffer will never return FALSE,\r
+ * so suspension need not be handled.\r
+ */\r
+ }\r
+ src->pub.next_input_byte += (size_t) num_bytes;\r
+ src->pub.bytes_in_buffer -= (size_t) num_bytes;\r
+ }\r
+}\r
+\r
+\r
+/*\r
+ * An additional method that can be provided by data source modules is the\r
+ * resync_to_restart method for error recovery in the presence of RST markers.\r
+ * For the moment, this source module just uses the default resync method\r
+ * provided by the JPEG library. That method assumes that no backtracking\r
+ * is possible.\r
+ */\r
+\r
+\r
+/*\r
+ * Terminate source --- called by jpeg_finish_decompress\r
+ * after all data has been read. Often a no-op.\r
+ *\r
+ * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding\r
+ * application must deal with any cleanup that should happen even\r
+ * for error exit.\r
+ */\r
+\r
+METHODDEF(void)\r
+term_source (j_decompress_ptr cinfo)\r
+{\r
+ /* no work necessary here */\r
+}\r
+\r
+\r
+/*\r
+ * Prepare for input from a memory buffer.\r
+ */\r
+\r
+GLOBAL(void)\r
+jpeg_memory_src (j_decompress_ptr cinfo, const JOCTET * buffer, size_t bufsize)\r
+{\r
+ my_src_ptr src;\r
+\r
+ /* The source object is made permanent so that a series of JPEG images\r
+ * can be read from a single buffer by calling jpeg_memory_src\r
+ * only before the first one.\r
+ * This makes it unsafe to use this manager and a different source\r
+ * manager serially with the same JPEG object. Caveat programmer.\r
+ */\r
+ if (cinfo->src == NULL) { /* first time for this JPEG object? */\r
+ cinfo->src = (struct jpeg_source_mgr *)\r
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,\r
+ SIZEOF(my_source_mgr));\r
+ }\r
+\r
+ src = (my_src_ptr) cinfo->src;\r
+ src->pub.init_source = init_source;\r
+ src->pub.fill_input_buffer = fill_input_buffer;\r
+ src->pub.skip_input_data = skip_input_data;\r
+ src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */\r
+ src->pub.term_source = term_source;\r
+\r
+ src->pub.next_input_byte = buffer;\r
+ src->pub.bytes_in_buffer = bufsize;\r
+}\r
+\r
+\r
projects / gdcm.git / commitdiff