Support multiple gzips in one gzip file.

BeebEm seems to emit UEF files that are multiple concatenated
gzip files.

util_compress.c

@@ -7,14 +7,19 @@
 
 #include <string.h>
 
-int
-util_gunzip(size_t* p_dst_len, uint8_t* p_src, size_t src_len, uint8_t* p_dst) {
+static int
+util_gunzip_chunk(size_t* p_dst_len,
+                  size_t* p_src_consumed,
+                  uint8_t* p_src,
+                  size_t src_len,
+                  uint8_t* p_dst) {
   z_stream stream;
   int status;
   uint8_t flags;
   size_t dst_len = *p_dst_len;
+  size_t src_left = src_len;
 
-  if (src_len < 10) {
+  if (src_left < 10) {
     return -100;
   }
   if ((p_src[0] != 0x1F) || (p_src[1] != 0x8B)) {
@@ -32,23 +37,23 @@ util_gunzip(size_t* p_dst_len, uint8_t* p_src, size_t src_len, uint8_t* p_dst) {
 
   /* Skip header. */
   p_src += 10;
-  src_len -= 10;
+  src_left -= 10;
 
   /* Skip filename if any. */
   if (flags & 0x08) {
-    while ((src_len > 0) && (*p_src != '\0')) {
+    while ((src_left > 0) && (*p_src != '\0')) {
       p_src++;
-      src_len--;
+      src_left--;
     }
-    if (src_len > 0) {
+    if (src_left > 0) {
       p_src++;
-      src_len--;
+      src_left--;
     }
   }
 
   (void) memset(&stream, '\0', sizeof(stream));
   stream.next_in = p_src;
-  stream.avail_in = src_len;
+  stream.avail_in = src_left;
   stream.next_out = p_dst;
   stream.avail_out = dst_len;
 
@@ -63,6 +68,8 @@ util_gunzip(size_t* p_dst_len, uint8_t* p_src, size_t src_len, uint8_t* p_dst) {
   }
 
   *p_dst_len = (dst_len - stream.avail_out);
+  src_left -= stream.total_in;
+  *p_src_consumed = (src_len - src_left);
 
   if (inflateEnd(&stream) != Z_OK) {
     return -3;
@@ -71,6 +78,43 @@ util_gunzip(size_t* p_dst_len, uint8_t* p_src, size_t src_len, uint8_t* p_dst) {
   return 0;
 }
 
+int
+util_gunzip(size_t* p_dst_len, uint8_t* p_src, size_t src_len, uint8_t* p_dst) {
+  size_t src_left = src_len;
+  size_t dst_left = *p_dst_len;
+  size_t dst_written = 0;
+  int ret;
+
+  while (1) {
+    size_t src_consumed = 0;
+    size_t dst_len = dst_left;
+    ret = util_gunzip_chunk(&dst_len, &src_consumed, p_src, src_left, p_dst);
+    if (ret != 0) {
+      break;
+    }
+
+    dst_written += dst_len;
+    dst_left -= dst_len;
+    p_dst += dst_len;
+    src_left -= src_consumed;
+    p_src += src_consumed;
+
+    /* Go again if there are more gzip headers in the expected place. BeebEm
+     * seems to emit UEF files that are multiple concatenated gzip files.
+     */
+    if ((src_left > 10) && (p_src[8] == 0x1f) && (p_src[9] == 0x8b)) {
+      src_left -= 8;
+      p_src += 8;
+      /* Go again. */
+    } else {
+      break;
+    }
+  }
+
+  *p_dst_len = dst_written;
+  return ret;
+}
+
 int
 util_uncompress(size_t* p_dst_len,
                 uint8_t* p_src,