lib/jpeg: return string (not int) error messages

Change-Id: I465a6eebc2a41ca9a618b1e86dee015cea40800b
Signed-off-by: Nigel Tao <nigeltao@golang.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84341
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

3 files changed, 30 insertions, 33 deletions

diff --git a/src/lib/bootsplash.c b/src/lib/bootsplash.c
index 38d0ce7c97..2ec0052bfa 100644
--- a/src/lib/bootsplash.c
+++ b/src/lib/bootsplash.c
@@ -28,8 +28,9 @@ void set_bootsplash(unsigned char *framebuffer, unsigned int x_resolution,
 	}
 
 	unsigned int image_width, image_height;
-	if (jpeg_fetch_size(jpeg, filesize, &image_width, &image_height) != 0) {
-		printk(BIOS_ERR, "Could not parse bootsplash.jpg\n");
+	const char *err = jpeg_fetch_size(jpeg, filesize, &image_width, &image_height);
+	if (err != NULL) {
+		printk(BIOS_ERR, "Could not parse bootsplash.jpg: %s\n", err);
 		return;
 	}
 
@@ -45,12 +46,11 @@ void set_bootsplash(unsigned char *framebuffer, unsigned int x_resolution,
 	framebuffer += (yres - image_height) / 2 * bytes_per_line
 		       + (xres - image_width) / 2 * (fb_resolution / 8);
 
-	int ret = jpeg_decode(jpeg, filesize, framebuffer, image_width, image_height,
-			      bytes_per_line, fb_resolution);
+	err = jpeg_decode(jpeg, filesize, framebuffer, image_width, image_height,
+			  bytes_per_line, fb_resolution);
 	cbfs_unmap(jpeg);
-	if (ret != 0) {
-		printk(BIOS_ERR, "Bootsplash could not be decoded. jpeg_decode returned %d.\n",
-		       ret);
+	if (err != NULL) {
+		printk(BIOS_ERR, "Could not decode bootsplash.jpg: %s\n", err);
 		return;
 	}
 	printk(BIOS_INFO, "Bootsplash loaded\n");
diff --git a/src/lib/jpeg.c b/src/lib/jpeg.c
index 617ab0b22a..d084c1a7a5 100644
--- a/src/lib/jpeg.c
+++ b/src/lib/jpeg.c
@@ -19,38 +19,38 @@
 /* ~16K is big enough to move this off the stack */
 static wuffs_jpeg__decoder dec;
 
-int jpeg_fetch_size(unsigned char *filedata, size_t filesize, unsigned int *width,
-		    unsigned int *height)
+const char *jpeg_fetch_size(unsigned char *filedata, size_t filesize, unsigned int *width,
+			    unsigned int *height)
 {
 	if (!width || !height) {
-		return JPEG_DECODE_FAILED;
+		return "invalid arg";
 	}
 
 	wuffs_base__status status = wuffs_jpeg__decoder__initialize(
 		&dec, sizeof(dec), WUFFS_VERSION, WUFFS_INITIALIZE__DEFAULT_OPTIONS);
 	if (status.repr) {
-		return JPEG_DECODE_FAILED;
+		return status.repr;
 	}
 
 	wuffs_base__image_config imgcfg;
 	wuffs_base__io_buffer src = wuffs_base__ptr_u8__reader(filedata, filesize, true);
 	status = wuffs_jpeg__decoder__decode_image_config(&dec, &imgcfg, &src);
 	if (status.repr) {
-		return JPEG_DECODE_FAILED;
+		return status.repr;
 	}
 
 	*width = wuffs_base__pixel_config__width(&imgcfg.pixcfg);
 	*height = wuffs_base__pixel_config__height(&imgcfg.pixcfg);
 
-	return 0;
+	return NULL;
 }
 
-int jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *pic,
-		unsigned int width, unsigned int height, unsigned int bytes_per_line,
-		unsigned int depth)
+const char *jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *pic,
+			unsigned int width, unsigned int height, unsigned int bytes_per_line,
+			unsigned int depth)
 {
 	if (!filedata || !pic) {
-		return JPEG_DECODE_FAILED;
+		return "invalid arg";
 	}
 	/* Relatively arbitrary limit that shouldn't hurt anybody.
 	 * 300M (10k*10k*3bytes/pixel) is already larger than our heap, so
@@ -59,7 +59,7 @@ int jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *pic,
 	 * calculations in this function.
 	 */
 	if ((width > 10000) || (height > 10000)) {
-		return JPEG_DECODE_FAILED;
+		return "invalid arg";
 	}
 
 	uint32_t pixfmt;
@@ -74,13 +74,13 @@ int jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *pic,
 		pixfmt = WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL;
 		break;
 	default:
-		return JPEG_DECODE_FAILED;
+		return "invalid arg";
 	}
 
 	wuffs_base__status status = wuffs_jpeg__decoder__initialize(
 		&dec, sizeof(dec), WUFFS_VERSION, WUFFS_INITIALIZE__DEFAULT_OPTIONS);
 	if (status.repr) {
-		return JPEG_DECODE_FAILED;
+		return status.repr;
 	}
 
 	/* Opting in to lower quality means that we can pass an empty slice as the
@@ -105,7 +105,7 @@ int jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *pic,
 	wuffs_base__io_buffer src = wuffs_base__ptr_u8__reader(filedata, filesize, true);
 	status = wuffs_jpeg__decoder__decode_image_config(&dec, &imgcfg, &src);
 	if (status.repr) {
-		return JPEG_DECODE_FAILED;
+		return status.repr;
 	}
 
 	wuffs_base__pixel_config pixcfg;
@@ -117,15 +117,11 @@ int jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *pic,
 		wuffs_base__make_table_u8(pic, width * (depth / 8), height, bytes_per_line),
 		wuffs_base__empty_slice_u8());
 	if (status.repr) {
-		return JPEG_DECODE_FAILED;
+		return status.repr;
 	}
 
 	status = wuffs_jpeg__decoder__decode_frame(&dec, &pixbuf, &src,
 						   WUFFS_BASE__PIXEL_BLEND__SRC,
 						   wuffs_base__empty_slice_u8(), NULL);
-	if (status.repr) {
-		return JPEG_DECODE_FAILED;
-	}
-
-	return 0;
+	return status.repr;
 }
diff --git a/src/lib/jpeg.h b/src/lib/jpeg.h
index d2e9e5ffcf..c5179c8c4f 100644
--- a/src/lib/jpeg.h
+++ b/src/lib/jpeg.h
@@ -5,12 +5,13 @@
 
 #include <stdlib.h>
 
-#define JPEG_DECODE_FAILED 1
+/* These functions return NULL on success and a short error message on
+ * failure. Callers should not free the returned pointer. */
 
-int jpeg_fetch_size(unsigned char *filedata, size_t filesize, unsigned int *width,
-		    unsigned int *height);
-int jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *framebuffer,
-		unsigned int width, unsigned int height, unsigned int bytes_per_line,
-		unsigned int depth);
+const char *jpeg_fetch_size(unsigned char *filedata, size_t filesize, unsigned int *width,
+			    unsigned int *height);
+const char *jpeg_decode(unsigned char *filedata, size_t filesize, unsigned char *framebuffer,
+			unsigned int width, unsigned int height, unsigned int bytes_per_line,
+			unsigned int depth);
 
 #endif