[Qemu-devel] [PATCH] fw_cfg: Use g_file_get_contents instead of multiple fread() calls

[Qemu-devel] [PATCH] fw_cfg: Use g_file_get_contents instead of multiple fread() calls

[Pavel Borzenkov]

Signed-off-by: Pavel Borzenkov <pavel.borzenkov@gmail.com>
---
 hw/fw_cfg.c |  100 ++++++++++++++++++++++-------------------------------------
 1 files changed, 37 insertions(+), 63 deletions(-)

diff --git a/hw/fw_cfg.c b/hw/fw_cfg.c
index 8df265c..d2400f5 100644
--- a/hw/fw_cfg.c
+++ b/hw/fw_cfg.c
@@ -60,71 +60,55 @@ struct FWCfgState {
 #define JPG_FILE 0
 #define BMP_FILE 1
 
-static FILE *probe_splashfile(char *filename, int *file_sizep, int *file_typep)
+static char *read_splashfile(char *filename, int *file_sizep, int *file_typep)
 {
-    FILE *fp = NULL;
-    int fop_ret;
-    int file_size;
+    GError *err = NULL;
+    gboolean res;
+    gchar *content;
     int file_type = -1;
-    unsigned char buf[2] = {0, 0};
-    unsigned int filehead_value = 0;
+    unsigned int filehead = 0;
     int bmp_bpp;
 
-    fp = fopen(filename, "rb");
-    if (fp == NULL) {
-        error_report("failed to open file '%s'.", filename);
-        return fp;
+    res = g_file_get_contents(filename, &content, (gsize *)file_sizep, &err);
+    if (res == FALSE) {
+        error_report("falied to read file '%s'", filename);
+        g_error_free(err);
+        return NULL;
     }
+
     /* check file size */
-    fseek(fp, 0L, SEEK_END);
-    file_size = ftell(fp);
-    if (file_size < 2) {
-        error_report("file size is less than 2 bytes '%s'.", filename);
-        fclose(fp);
-        fp = NULL;
-        return fp;
+    if (*file_sizep < 30) {
+        error_report("file size is less than 30 bytes '%s'", filename);
+        g_free(content);
+        return NULL;
     }
+
     /* check magic ID */
-    fseek(fp, 0L, SEEK_SET);
-    fop_ret = fread(buf, 1, 2, fp);
-    if (fop_ret != 2) {
-        error_report("Could not read header from '%s': %s",
-                     filename, strerror(errno));
-        fclose(fp);
-        fp = NULL;
-        return fp;
-    }
-    filehead_value = (buf[0] + (buf[1] << 8)) & 0xffff;
-    if (filehead_value == 0xd8ff) {
+    filehead = ((content[0] & 0xff) + (content[1] << 8)) & 0xffff;
+    if (filehead == 0xd8ff) {
         file_type = JPG_FILE;
+    } else if (filehead == 0x4d42) {
+        file_type = BMP_FILE;
     } else {
-        if (filehead_value == 0x4d42) {
-            file_type = BMP_FILE;
-        }
-    }
-    if (file_type < 0) {
-        error_report("'%s' not jpg/bmp file,head:0x%x.",
-                         filename, filehead_value);
-        fclose(fp);
-        fp = NULL;
-        return fp;
+        error_report("'%s' not jpg/bmp file, head:0x%x.", filename, filehead);
+        g_free(content);
+        return NULL;
     }
+
     /* check BMP bpp */
     if (file_type == BMP_FILE) {
-        fseek(fp, 28, SEEK_SET);
-        fop_ret = fread(buf, 1, 2, fp);
-        bmp_bpp = (buf[0] + (buf[1] << 8)) & 0xffff;
+        bmp_bpp = (content[28] + (content[29] << 8)) & 0xffff;
         if (bmp_bpp != 24) {
             error_report("only 24bpp bmp file is supported.");
-            fclose(fp);
-            fp = NULL;
-            return fp;
+            g_free(content);
+            return NULL;
         }
     }
+
     /* return values */
-    *file_sizep = file_size;
     *file_typep = file_type;
-    return fp;
+
+    return content;
 }
 
 static void fw_cfg_bootsplash(FWCfgState *s)
@@ -132,9 +116,7 @@ static void fw_cfg_bootsplash(FWCfgState *s)
     int boot_splash_time = -1;
     const char *boot_splash_filename = NULL;
     char *p;
-    char *filename;
-    FILE *fp;
-    int fop_ret;
+    char *filename, *file_data;
     int file_size;
     int file_type = -1;
     const char *temp;
@@ -174,27 +156,19 @@ static void fw_cfg_bootsplash(FWCfgState *s)
             error_report("failed to find file '%s'.", boot_splash_filename);
             return;
         }
-        /* probing the file */
-        fp = probe_splashfile(filename, &file_size, &file_type);
-        if (fp == NULL) {
+
+        /* loading file data */
+        file_data = read_splashfile(filename, &file_size, &file_type);
+        if (file_data == NULL) {
             g_free(filename);
             return;
         }
-        /* loading file data */
         if (boot_splash_filedata != NULL) {
             g_free(boot_splash_filedata);
         }
-        boot_splash_filedata = g_malloc(file_size);
+        boot_splash_filedata = (uint8_t *)file_data;
         boot_splash_filedata_size = file_size;
-        fseek(fp, 0L, SEEK_SET);
-        fop_ret = fread(boot_splash_filedata, 1, file_size, fp);
-        if (fop_ret != file_size) {
-            error_report("failed to read data from '%s'.",
-                         boot_splash_filename);
-            fclose(fp);
-            return;
-        }
-        fclose(fp);
+
         /* insert data */
         if (file_type == JPG_FILE) {
             fw_cfg_add_file(s, "bootsplash.jpg",
-- 
1.7.0.4

Re: [Qemu-devel] [PATCH] fw_cfg: Use g_file_get_contents instead of multiple fread() calls

[Peter Maydell]

On 21 October 2011 12:35, Pavel Borzenkov <pavel.borzenkov@gmail.com> wrote:
> Signed-off-by: Pavel Borzenkov <pavel.borzenkov@gmail.com>

Thanks; I think this looks a lot nicer than the raw file ops code did.
I think we could probably make the error messages slightly more user
friendly while we're here.

> +    res = g_file_get_contents(filename, &content, (gsize *)file_sizep, &err);
> +    if (res == FALSE) {
> +        error_report("falied to read file '%s'", filename);

You've made a typo here ("failed"); also I think all the error messages
in this function should say "splash file" rather than just "file",
and include the filename.

> +    if (*file_sizep < 30) {
> +        error_report("file size is less than 30 bytes '%s'", filename);
> +        g_free(content);
> +        return NULL;

Rather than saying exactly what check failed (the user won't care)
we should just say "splash file '%s' format not recognized; must be JPEG
or 24 bit BMP".

> +        error_report("'%s' not jpg/bmp file, head:0x%x.", filename, filehead);

and here also.

>         if (bmp_bpp != 24) {
>             error_report("only 24bpp bmp file is supported.");

and here I think.

-- PMM