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1 /*
2  * jdatasrc.c
3  *
4  * This file was part of the Independent JPEG Group's software:
5  * Copyright (C) 1994-1996, Thomas G. Lane.
6  * Modified 2009-2011 by Guido Vollbeding.
7  * libjpeg-turbo Modifications:
8  * Copyright (C) 2013, 2016, D. R. Commander.
9  * For conditions of distribution and use, see the accompanying README.ijg
10  * file.
11  *
12  * This file contains decompression data source routines for the case of
13  * reading JPEG data from memory or from a file (or any stdio stream).
14  * While these routines are sufficient for most applications,
15  * some will want to use a different source manager.
16  * IMPORTANT: we assume that fread() will correctly transcribe an array of
17  * JOCTETs from 8-bit-wide elements on external storage.  If char is wider
18  * than 8 bits on your machine, you may need to do some tweaking.
19  */
20 
21 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
22 #include "jinclude.h"
23 #include "jpeglib.h"
24 #include "jerror.h"
25 
26 
27 /* Expanded data source object for stdio input */
28 
29 typedef struct {
30   struct jpeg_source_mgr pub;   /* public fields */
31 
32   FILE *infile;                 /* source stream */
33   JOCTET *buffer;               /* start of buffer */
34   boolean start_of_file;        /* have we gotten any data yet? */
35 } my_source_mgr;
36 
37 typedef my_source_mgr *my_src_ptr;
38 
39 #define INPUT_BUF_SIZE  4096    /* choose an efficiently fread'able size */
40 
41 
42 /*
43  * Initialize source --- called by jpeg_read_header
44  * before any data is actually read.
45  */
46 
47 METHODDEF(void)
init_source(j_decompress_ptr cinfo)48 init_source(j_decompress_ptr cinfo)
49 {
50   my_src_ptr src = (my_src_ptr)cinfo->src;
51 
52   /* We reset the empty-input-file flag for each image,
53    * but we don't clear the input buffer.
54    * This is correct behavior for reading a series of images from one source.
55    */
56   src->start_of_file = TRUE;
57 }
58 
59 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
60 METHODDEF(void)
init_mem_source(j_decompress_ptr cinfo)61 init_mem_source(j_decompress_ptr cinfo)
62 {
63   /* no work necessary here */
64 }
65 #endif
66 
67 
68 /*
69  * Fill the input buffer --- called whenever buffer is emptied.
70  *
71  * In typical applications, this should read fresh data into the buffer
72  * (ignoring the current state of next_input_byte & bytes_in_buffer),
73  * reset the pointer & count to the start of the buffer, and return TRUE
74  * indicating that the buffer has been reloaded.  It is not necessary to
75  * fill the buffer entirely, only to obtain at least one more byte.
76  *
77  * There is no such thing as an EOF return.  If the end of the file has been
78  * reached, the routine has a choice of ERREXIT() or inserting fake data into
79  * the buffer.  In most cases, generating a warning message and inserting a
80  * fake EOI marker is the best course of action --- this will allow the
81  * decompressor to output however much of the image is there.  However,
82  * the resulting error message is misleading if the real problem is an empty
83  * input file, so we handle that case specially.
84  *
85  * In applications that need to be able to suspend compression due to input
86  * not being available yet, a FALSE return indicates that no more data can be
87  * obtained right now, but more may be forthcoming later.  In this situation,
88  * the decompressor will return to its caller (with an indication of the
89  * number of scanlines it has read, if any).  The application should resume
90  * decompression after it has loaded more data into the input buffer.  Note
91  * that there are substantial restrictions on the use of suspension --- see
92  * the documentation.
93  *
94  * When suspending, the decompressor will back up to a convenient restart point
95  * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
96  * indicate where the restart point will be if the current call returns FALSE.
97  * Data beyond this point must be rescanned after resumption, so move it to
98  * the front of the buffer rather than discarding it.
99  */
100 
101 METHODDEF(boolean)
fill_input_buffer(j_decompress_ptr cinfo)102 fill_input_buffer(j_decompress_ptr cinfo)
103 {
104   my_src_ptr src = (my_src_ptr)cinfo->src;
105   size_t nbytes;
106 
107   nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
108 
109   if (nbytes <= 0) {
110     if (src->start_of_file)     /* Treat empty input file as fatal error */
111       ERREXIT(cinfo, JERR_INPUT_EMPTY);
112     WARNMS(cinfo, JWRN_JPEG_EOF);
113     /* Insert a fake EOI marker */
114     src->buffer[0] = (JOCTET)0xFF;
115     src->buffer[1] = (JOCTET)JPEG_EOI;
116     nbytes = 2;
117   }
118 
119   src->pub.next_input_byte = src->buffer;
120   src->pub.bytes_in_buffer = nbytes;
121   src->start_of_file = FALSE;
122 
123   return TRUE;
124 }
125 
126 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
127 METHODDEF(boolean)
fill_mem_input_buffer(j_decompress_ptr cinfo)128 fill_mem_input_buffer(j_decompress_ptr cinfo)
129 {
130   static const JOCTET mybuffer[4] = {
131     (JOCTET)0xFF, (JOCTET)JPEG_EOI, 0, 0
132   };
133 
134   /* The whole JPEG data is expected to reside in the supplied memory
135    * buffer, so any request for more data beyond the given buffer size
136    * is treated as an error.
137    */
138   WARNMS(cinfo, JWRN_JPEG_EOF);
139 
140   /* Insert a fake EOI marker */
141 
142   cinfo->src->next_input_byte = mybuffer;
143   cinfo->src->bytes_in_buffer = 2;
144 
145   return TRUE;
146 }
147 #endif
148 
149 
150 /*
151  * Skip data --- used to skip over a potentially large amount of
152  * uninteresting data (such as an APPn marker).
153  *
154  * Writers of suspendable-input applications must note that skip_input_data
155  * is not granted the right to give a suspension return.  If the skip extends
156  * beyond the data currently in the buffer, the buffer can be marked empty so
157  * that the next read will cause a fill_input_buffer call that can suspend.
158  * Arranging for additional bytes to be discarded before reloading the input
159  * buffer is the application writer's problem.
160  */
161 
162 METHODDEF(void)
skip_input_data(j_decompress_ptr cinfo,long num_bytes)163 skip_input_data(j_decompress_ptr cinfo, long num_bytes)
164 {
165   struct jpeg_source_mgr *src = cinfo->src;
166 
167   /* Just a dumb implementation for now.  Could use fseek() except
168    * it doesn't work on pipes.  Not clear that being smart is worth
169    * any trouble anyway --- large skips are infrequent.
170    */
171   if (num_bytes > 0) {
172     while (num_bytes > (long)src->bytes_in_buffer) {
173       num_bytes -= (long)src->bytes_in_buffer;
174       (void)(*src->fill_input_buffer) (cinfo);
175       /* note we assume that fill_input_buffer will never return FALSE,
176        * so suspension need not be handled.
177        */
178     }
179     src->next_input_byte += (size_t)num_bytes;
180     src->bytes_in_buffer -= (size_t)num_bytes;
181   }
182 }
183 
184 
185 /*
186  * An additional method that can be provided by data source modules is the
187  * resync_to_restart method for error recovery in the presence of RST markers.
188  * For the moment, this source module just uses the default resync method
189  * provided by the JPEG library.  That method assumes that no backtracking
190  * is possible.
191  */
192 
193 
194 /*
195  * Terminate source --- called by jpeg_finish_decompress
196  * after all data has been read.  Often a no-op.
197  *
198  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
199  * application must deal with any cleanup that should happen even
200  * for error exit.
201  */
202 
203 METHODDEF(void)
term_source(j_decompress_ptr cinfo)204 term_source(j_decompress_ptr cinfo)
205 {
206   /* no work necessary here */
207 }
208 
209 
210 /*
211  * Prepare for input from a stdio stream.
212  * The caller must have already opened the stream, and is responsible
213  * for closing it after finishing decompression.
214  */
215 
216 GLOBAL(void)
jpeg_stdio_src(j_decompress_ptr cinfo,FILE * infile)217 jpeg_stdio_src(j_decompress_ptr cinfo, FILE *infile)
218 {
219   my_src_ptr src;
220 
221   /* The source object and input buffer are made permanent so that a series
222    * of JPEG images can be read from the same file by calling jpeg_stdio_src
223    * only before the first one.  (If we discarded the buffer at the end of
224    * one image, we'd likely lose the start of the next one.)
225    */
226   if (cinfo->src == NULL) {     /* first time for this JPEG object? */
227     cinfo->src = (struct jpeg_source_mgr *)
228       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
229                                   sizeof(my_source_mgr));
230     src = (my_src_ptr)cinfo->src;
231     src->buffer = (JOCTET *)
232       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
233                                   INPUT_BUF_SIZE * sizeof(JOCTET));
234   } else if (cinfo->src->init_source != init_source) {
235     /* It is unsafe to reuse the existing source manager unless it was created
236      * by this function.  Otherwise, there is no guarantee that the opaque
237      * structure is the right size.  Note that we could just create a new
238      * structure, but the old structure would not be freed until
239      * jpeg_destroy_decompress() was called.
240      */
241     ERREXIT(cinfo, JERR_BUFFER_SIZE);
242   }
243 
244   src = (my_src_ptr)cinfo->src;
245   src->pub.init_source = init_source;
246   src->pub.fill_input_buffer = fill_input_buffer;
247   src->pub.skip_input_data = skip_input_data;
248   src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
249   src->pub.term_source = term_source;
250   src->infile = infile;
251   src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
252   src->pub.next_input_byte = NULL; /* until buffer loaded */
253 }
254 
255 
256 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
257 /*
258  * Prepare for input from a supplied memory buffer.
259  * The buffer must contain the whole JPEG data.
260  */
261 
262 GLOBAL(void)
jpeg_mem_src(j_decompress_ptr cinfo,const unsigned char * inbuffer,unsigned long insize)263 jpeg_mem_src(j_decompress_ptr cinfo, const unsigned char *inbuffer,
264              unsigned long insize)
265 {
266   struct jpeg_source_mgr *src;
267 
268   if (inbuffer == NULL || insize == 0)  /* Treat empty input as fatal error */
269     ERREXIT(cinfo, JERR_INPUT_EMPTY);
270 
271   /* The source object is made permanent so that a series of JPEG images
272    * can be read from the same buffer by calling jpeg_mem_src only before
273    * the first one.
274    */
275   if (cinfo->src == NULL) {     /* first time for this JPEG object? */
276     cinfo->src = (struct jpeg_source_mgr *)
277       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
278                                   sizeof(struct jpeg_source_mgr));
279   } else if (cinfo->src->init_source != init_mem_source) {
280     /* It is unsafe to reuse the existing source manager unless it was created
281      * by this function.
282      */
283     ERREXIT(cinfo, JERR_BUFFER_SIZE);
284   }
285 
286   src = cinfo->src;
287   src->init_source = init_mem_source;
288   src->fill_input_buffer = fill_mem_input_buffer;
289   src->skip_input_data = skip_input_data;
290   src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
291   src->term_source = term_source;
292   src->bytes_in_buffer = (size_t)insize;
293   src->next_input_byte = (const JOCTET *)inbuffer;
294 }
295 #endif
296