forgot to add yesterday :/

I/O plugin for libjpg that reads from memory

This was SVN commit r1661.

source/lib/res/jmemdatasrc.cpp

@@ -0,0 +1,186 @@
+#include "precompiled.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * jmemdatasrc.c (adapted from IJG jdatasrc.c)
+ *
+ * Copyright (C) 2004, Jan Wassenberg.
+ * Copyright (C) 1994-1996, Thomas G. Lane.
+ *
+ * This file contains decompression data source routines for the case of
+ * reading JPEG data from a single memory buffer. Suspension isn't used.
+ *
+ * IMPORTANT: we assume that JOCTET is 8 bits.
+ */
+
+/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
+#include "jinclude.h"
+#include "jpeglib.h"
+#include "jerror.h"
+
+
+/* Expanded data source object for memory input */
+typedef struct
+{
+	struct jpeg_source_mgr pub;	/* public fields */
+
+	JOCTET* buf;
+	size_t size;	/* total size (bytes) */
+	size_t pos;		/* offset (bytes) to new data */
+}
+MemSrcMgr;
+
+typedef MemSrcMgr* SrcPtr;
+
+
+/*
+ * Initialize source --- called by jpeg_read_header
+ * before any data is actually read.
+ */
+
+METHODDEF(void) init_source(j_decompress_ptr cinfo)
+{
+}
+
+
+/*
+ * Fill the input buffer --- called whenever buffer is emptied.
+ *
+ * In typical applications, this should read fresh data into the buffer
+ * (ignoring the current state of next_input_byte & bytes_in_buffer),
+ * reset the pointer & count to the start of the buffer, and return TRUE
+ * indicating that the buffer has been reloaded.  It is not necessary to
+ * fill the buffer entirely, only to obtain at least one more byte.
+ *
+ * There is no such thing as an EOF return.  If the end of the file has been
+ * reached, the routine has a choice of ERREXIT() or inserting fake data into
+ * the buffer.  In most cases, generating a warning message and inserting a
+ * fake EOI marker is the best course of action --- this will allow the
+ * decompressor to output however much of the image is there.  However,
+ * the resulting error message is misleading if the real problem is an empty
+ * input file, so we handle that case specially.
+ */
+
+METHODDEF(boolean) fill_input_buffer(j_decompress_ptr cinfo)
+{
+	SrcPtr src = (SrcPtr)cinfo->src;
+	static const JOCTET eoi[2] = { 0xFF, JPEG_EOI };
+
+	/*
+	 * since jpeg_mem_src fills the buffer with everything we've got,
+	 * jpeg is trying to read beyond end of buffer. return a fake EOI marker.
+	 * note: don't modify input buffer: it might be read-only.
+	 */
+
+	WARNMS(cinfo, JWRN_JPEG_EOF);
+
+
+	src->pub.next_input_byte = eoi;
+	src->pub.bytes_in_buffer = 2;
+	return TRUE;
+}
+
+
+/*
+ * Skip data --- used to skip over a potentially large amount of
+ * uninteresting data (such as an APPn marker).
+ */
+
+METHODDEF(void) skip_input_data(j_decompress_ptr cinfo, long num_bytes)
+{
+	SrcPtr src = (SrcPtr)cinfo->src;
+	size_t skip_count = (size_t)num_bytes;
+
+	/* docs say non-positive num_byte skips should be ignored */
+	if(num_bytes <= 0)
+		return;
+
+	/*
+	 * just subtract bytes available in buffer,
+	 * making sure we don't underflow the size_t.
+	 * note: if we skip to or beyond end of buffer,
+	 * bytes_in_buffer = 0 => fill_input_buffer called => abort.
+	 */
+	if(skip_count > src->pub.bytes_in_buffer)
+		skip_count = src->pub.bytes_in_buffer;
+
+	src->pub.bytes_in_buffer -= skip_count;
+	src->pub.next_input_byte += skip_count;
+}
+
+
+/*
+ * An additional method that can be provided by data source modules is the
+ * resync_to_restart method for error recovery in the presence of RST markers.
+ * For the moment, this source module just uses the default resync method
+ * provided by the JPEG library.  That method assumes that no backtracking
+ * is possible.
+ */
+
+
+/*
+ * Terminate source --- called by jpeg_finish_decompress
+ * after all data has been read.  Often a no-op.
+ *
+ * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
+ * application must deal with any cleanup that should happen even
+ * for error exit.
+ */
+
+METHODDEF(void) term_source(j_decompress_ptr cinfo)
+{
+	/*
+	 * no-op (we don't own the buffer and shouldn't,
+	 * to make possible multiple images in a source).
+	 */
+}
+
+
+/*
+ * Prepare for input from a buffer.
+ * The caller is responsible for freeing it after finishing decompression.
+ */
+
+GLOBAL(void) jpeg_mem_src(j_decompress_ptr cinfo, void* p, size_t size)
+{
+	SrcPtr src;
+
+	/* Treat 0-length buffer as fatal error */
+	if(size == 0)
+		ERREXIT(cinfo, JERR_INPUT_EMPTY);
+
+	/*
+	 * The source object is made permanent so that
+	 * a series of JPEG images can be read from the same file
+	 * by calling jpeg_mem_src only before the first one.
+	 * This makes it unsafe to use this manager and a different source
+	 * manager serially with the same JPEG object.  Caveat programmer.
+
+	/* first time for this JPEG object? */
+	if(!cinfo->src)
+		cinfo->src = (struct jpeg_source_mgr*)
+			(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
+				SIZEOF(MemSrcMgr));
+			/* (takes care of raising error if out of memory) */
+
+	src = (SrcPtr)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; /* default */
+	src->pub.term_source       = term_source;
+
+	/*
+	 * fill buffer with everything we have.
+	 * if fill_input_buffer is called, the buffer was overrun.
+	 */
+	src->pub.bytes_in_buffer   = size;
+	src->pub.next_input_byte   = (JOCTET*)p;
+}
+
+#ifdef __cplusplus
+}
+#endif