Comboot/Com32 changes for unspecified file lengths

Handle unspecified file length for comboot/com32 modules; do changes
to the appropriate part of libcom32 to handle this properly.

1 files changed, 65 insertions, 26 deletions

diff --git a/com32/lib/syslinux/loadfile.c b/com32/lib/syslinux/loadfile.c
index ec7a6039..f5479dab 100644
--- a/com32/lib/syslinux/loadfile.c
+++ b/com32/lib/syslinux/loadfile.c
@@ -25,45 +25,84 @@
 
 #include <syslinux/loadfile.h>
 
+#define INCREMENTAL_CHUNK 1024*1024
+
 int loadfile(const char *filename, void **ptr, size_t *len)
 {
-  int fd;
-  struct stat st;
-  void *data;
   FILE *f;
-  size_t xlen;
+  int rv;
 
-  fd = open(filename, O_RDONLY);
-  if ( fd < 0 )
+  f = fopen(filename, "r");
+  if ( !f )
     return -1;
 
-  f = fdopen(fd, "rb");
-  if ( !f ) {
-    close(fd);
-    return -1;
-  }
+  rv = floadfile(f, ptr, len, NULL, 0);
+  fclose(f);
 
-  if ( fstat(fd, &st) )
-    goto err_fclose;
+  return rv;
+}
 
-  *len = st.st_size;
-  xlen = (st.st_size + LOADFILE_ZERO_PAD-1) & ~(LOADFILE_ZERO_PAD-1);
+int floadfile(FILE *f, void **ptr, size_t *len, const void *prefix,
+	      size_t prefix_len)
+{
+  struct stat st;
+  void *data, *dp;
+  size_t alen, clen, rlen, xlen;
 
-  *ptr = data = malloc(xlen);
-  if ( !data )
-    goto err_fclose;
+  clen = alen = 0;
+  data = NULL;
 
-  if ( (off_t)fread(data, 1, st.st_size, f) != st.st_size )
-    goto err_free;
+  if ( fstat(fileno(f), &st) )
+    goto err;
 
-  memset((char *)data + st.st_size, 0, xlen-st.st_size);
+  if (!S_ISREG(st.st_mode)) {
+    /* Not a regular file, we can't assume we know the file size */
+    if (prefix_len) {
+      clen = alen = prefix_len;
+      data = malloc(prefix_len);
+      if (!data)
+	goto err;
 
-  fclose(f);
+      memcpy(data, prefix, prefix_len);
+    }
+
+    do {
+      alen += INCREMENTAL_CHUNK;
+      dp = realloc(data, alen);
+      if (!dp)
+	goto err;
+      data = dp;
+
+      rlen = fread((char *)data+clen, 1, alen-clen, f);
+      clen += rlen;
+    } while (clen == alen);
+
+    *len = clen;
+    xlen = (clen + LOADFILE_ZERO_PAD-1) & ~(LOADFILE_ZERO_PAD-1);
+    dp = realloc(data, xlen);
+    if (dp)
+      data = dp;
+    *ptr = data;
+  } else {
+    *len = clen = st.st_size + prefix_len - ftell(f);
+    xlen = (clen + LOADFILE_ZERO_PAD-1) & ~(LOADFILE_ZERO_PAD-1);
+
+    *ptr = data = malloc(xlen);
+    if ( !data )
+      return -1;
+
+    memcpy(data, prefix, prefix_len);
+
+    if ( (off_t)fread((char *)data+prefix_len, 1, clen-prefix_len, f)
+	 != clen-prefix_len )
+      goto err;
+  }
+
+  memset((char *)data + clen, 0, xlen-clen);
   return 0;
 
- err_free:
-  free(data);
- err_fclose:
-  fclose(f);
+ err:
+  if (data)
+    free(data);
   return -1;
 }