Refactor djpeg.c to provide test interface

djpeg.c contains a standalone program to decode JPEG images. One use
of djpeg is to generate input for libjpeg-turbo unit tests.

This commit refactors djpeg.c to provide an interface to run the
djpeg code programmatically. A gtest wrapper containing JPEG
decompression unit tests will be introduced in a subsequent commit.

Bug: 993876
Change-Id: I22e35b14b14968156dae9c74785c5e95e2c0c3cb

2 files changed, 13 insertions, 9 deletions

diff --git a/README.chromium b/README.chromium
index b5db62e..1a3fe63 100644
--- a/README.chromium
+++ b/README.chromium
@@ -85,6 +85,7 @@ following changes which are not merged to upstream:
   - Refactor jpegtran.c to provide test interface
   - Add input JPEG images for djpeg and jpegtran tests
   - Add gtest wrapper for jpegtran tests
+  - Refactor djpeg.c to provide test interface
 
 Refer to working-with-nested-repos [1] for details of how to setup your git
 svn client to update the code (for making local changes, cherry picking from
diff --git a/djpeg.c b/djpeg.c
index 920e90d..acacfcb 100644
--- a/djpeg.c
+++ b/djpeg.c
@@ -504,7 +504,11 @@ print_text_marker(j_decompress_ptr cinfo)
  */
 
 int
+#ifdef GTEST
+djpeg(int argc, char **argv)
+#else
 main(int argc, char **argv)
+#endif
 {
   struct jpeg_decompress_struct cinfo;
   struct jpeg_error_mgr jerr;
@@ -583,7 +587,7 @@ main(int argc, char **argv)
   if (file_index < argc) {
     if ((input_file = fopen(argv[file_index], READ_BINARY)) == NULL) {
       fprintf(stderr, "%s: can't open %s\n", progname, argv[file_index]);
-      exit(EXIT_FAILURE);
+      return EXIT_FAILURE;
     }
   } else {
     /* default input file is stdin */
@@ -594,7 +598,7 @@ main(int argc, char **argv)
   if (outfilename != NULL) {
     if ((output_file = fopen(outfilename, WRITE_BINARY)) == NULL) {
       fprintf(stderr, "%s: can't open %s\n", progname, outfilename);
-      exit(EXIT_FAILURE);
+      return EXIT_FAILURE;
     }
   } else {
     /* default output file is stdout */
@@ -613,7 +617,7 @@ main(int argc, char **argv)
       inbuffer = (unsigned char *)realloc(inbuffer, insize + INPUT_BUF_SIZE);
       if (inbuffer == NULL) {
         fprintf(stderr, "%s: memory allocation failure\n", progname);
-        exit(EXIT_FAILURE);
+        return EXIT_FAILURE;
       }
       nbytes = JFREAD(input_file, &inbuffer[insize], INPUT_BUF_SIZE);
       if (nbytes < INPUT_BUF_SIZE && ferror(input_file)) {
@@ -689,7 +693,7 @@ main(int argc, char **argv)
     if (skip_end > cinfo.output_height - 1) {
       fprintf(stderr, "%s: skip region exceeds image height %d\n", progname,
               cinfo.output_height);
-      exit(EXIT_FAILURE);
+      return EXIT_FAILURE;
     }
 
     /* Write output file header.  This is a hack to ensure that the destination
@@ -724,7 +728,7 @@ main(int argc, char **argv)
         crop_y + crop_height > cinfo.output_height) {
       fprintf(stderr, "%s: crop dimensions exceed image dimensions %d x %d\n",
               progname, cinfo.output_width, cinfo.output_height);
-      exit(EXIT_FAILURE);
+      return EXIT_FAILURE;
     }
 
     jpeg_crop_scanline(&cinfo, &crop_x, &crop_width);
@@ -777,7 +781,7 @@ main(int argc, char **argv)
 
     if ((icc_file = fopen(icc_filename, WRITE_BINARY)) == NULL) {
       fprintf(stderr, "%s: can't open %s\n", progname, icc_filename);
-      exit(EXIT_FAILURE);
+      return EXIT_FAILURE;
     }
     if (jpeg_read_icc_profile(&cinfo, &icc_profile, &icc_len)) {
       if (fwrite(icc_profile, icc_len, 1, icc_file) < 1) {
@@ -785,7 +789,7 @@ main(int argc, char **argv)
                 icc_filename);
         free(icc_profile);
         fclose(icc_file);
-        exit(EXIT_FAILURE);
+        return EXIT_FAILURE;
       }
       free(icc_profile);
       fclose(icc_file);
@@ -815,6 +819,5 @@ main(int argc, char **argv)
     free(inbuffer);
 
   /* All done. */
-  exit(jerr.num_warnings ? EXIT_WARNING : EXIT_SUCCESS);
-  return 0;                     /* suppress no-return-value warnings */
+  return (jerr.num_warnings ? EXIT_WARNING : EXIT_SUCCESS);
 }