add prs_readblob (no unit tests yet)

buffer/prs_readblob.c

@@ -0,0 +1,38 @@
+#include "parse.h"
+
+static const size_t max_ssize_t = (((size_t)1) << (sizeof(size_t)*8-1))-1;
+
+/* Read n bytes from stream. Return n.
+ * Set stream to error state if not enough space or I/O error. */
+ssize_t prs_readblob(struct bytestream* bs,unsigned char* dest,size_t destlen) {
+  ssize_t r;
+  if (destlen > max_ssize_t)
+    destlen = max_ssize_t;
+  if (!bs_capacityassert(bs,destlen)) return -1;
+  r = destlen;
+
+  switch (bs->type) {
+
+  case MEMBUF:
+    memcpy(dest, bs->u.base+bs->cur, destlen);
+    bs->cur += destlen;
+    break;
+
+  case IOBUF:
+    buffer_get(bs->u.b, (char*)dest, destlen);
+    break;
+
+  case BSTREAM:
+    bs->cur += destlen;
+    r=prs_readblob(bs->u.bs, dest, destlen);
+    if (r != (ssize_t)destlen) {
+      bs->cur = 1;	// set bytestream to error state
+      bs->max = 0;
+      return -1;
+    }
+    break;
+
+  }
+
+    return r;
+}

parse.h

@@ -90,7 +90,7 @@ int bs_capacityassert(struct bytestream* bs,size_t capacity);
 
 /* Read n bytes from stream. Return n.
  * Set stream to error state if not enough space or I/O error. */
-size_t prs_readblob(struct bytestream* bs,unsigned char* dest,size_t destlen);
+ssize_t prs_readblob(struct bytestream* bs,unsigned char* dest,size_t destlen);
 
 uint16_t prs_u16(struct bytestream* bs);
 uint16_t prs_u16_big(struct bytestream* bs);