Add an error check for correct formatting in Deflate uncompressed

[sgt/halibut] / deflate.h

diff --git a/deflate.h b/deflate.h
index fac63e2..6f51407 100644 (file)
--- a/deflate.h
+++ b/deflate.h
@@ -6,9 +6,33 @@
 #ifndef DEFLATE_DEFLATE_H
 #define DEFLATE_DEFLATE_H
 
+/*
+ * Types of Deflate data stream.
+ * 
+ * DEFLATE_TYPE_BARE represents the basic Deflate data format, as
+ * defined in RFC 1951. It has no checksum to detect errors and no
+ * magic-number header for ease of recognition, but it does have
+ * internal EOF indication.
+ * 
+ * DEFLATE_TYPE_ZLIB represents the zlib container format, as
+ * defined in RFC 1950. It has a two-byte header, and a four-byte
+ * Adler32 checksum at the end to verify correct decoding, but
+ * apart from those six bytes it's exactly equivalent to
+ * DEFLATE_TYPE_BARE.
+ * 
+ * DEFLATE_TYPE_GZIP represents the gzip compressed file format, as
+ * defined in RFC 1952. This is a more full-featured format, with a
+ * magic number, a CRC checksum of the compressed data, and various
+ * header features including storing the original filename. This
+ * implementation accepts but ignores all of those features on
+ * input except the checksum, and outputs them in the most trivial
+ * fashion. Also, this implementation will not decode multiple
+ * concatenated gzip members (permitted by the RFC).
+ */
 enum {
     DEFLATE_TYPE_BARE,
-    DEFLATE_TYPE_ZLIB
+    DEFLATE_TYPE_ZLIB,
+    DEFLATE_TYPE_GZIP
 };
 
 /* ----------------------------------------------------------------------
@@ -60,9 +84,9 @@ void deflate_compress_free(deflate_compress_ctx *ctx);
  *    compressed data stream is cleaned up. Any checksums required
  *    at the end of the stream are also output.
  */
-int deflate_compress_data(deflate_compress_ctx *ctx,
-                         const void *inblock, int inlen, int flushtype,
-                         void **outblock, int *outlen);
+void deflate_compress_data(deflate_compress_ctx *ctx,
+                          const void *inblock, int inlen, int flushtype,
+                          void **outblock, int *outlen);
 
 enum {
     DEFLATE_NO_FLUSH,
@@ -99,10 +123,47 @@ void deflate_decompress_free(deflate_decompress_ctx *ctx);
  * that memory is stored in `outblock', and the length of output
  * data is stored in `outlen'.
  *
- * FIXME: error reporting?
+ * Returns 0 on success, or a non-zero error code if there was a
+ * decoding error. In case of an error return, the data decoded
+ * before the error is still returned as well. The possible errors
+ * are listed below.
+ * 
+ * If you want to check that the compressed data stream was
+ * correctly terminated, you can call this function with inlen==0
+ * to signal input EOF and see if an error comes back. If you don't
+ * care, don't bother.
  */
 int deflate_decompress_data(deflate_decompress_ctx *ctx,
                            const void *inblock, int inlen,
                            void **outblock, int *outlen);
 
+/*
+ * Enumeration of error codes. The strange macro is so that I can
+ * define description arrays in the accompanying source.
+ */
+#define DEFLATE_ERRORLIST(A) \
+    A(DEFLATE_NO_ERR, "success"), \
+    A(DEFLATE_ERR_ZLIB_HEADER, "invalid zlib header"), \
+    A(DEFLATE_ERR_ZLIB_WRONGCOMP, "zlib header specifies non-deflate compression"), \
+    A(DEFLATE_ERR_GZIP_HEADER, "invalid gzip header"), \
+    A(DEFLATE_ERR_GZIP_WRONGCOMP, "gzip header specifies non-deflate compression"), \
+    A(DEFLATE_ERR_GZIP_FHCRC, "gzip header specifies disputed FHCRC flag"), \
+    A(DEFLATE_ERR_SMALL_HUFTABLE, "under-committed Huffman code space"), \
+    A(DEFLATE_ERR_LARGE_HUFTABLE, "over-committed Huffman code space"), \
+    A(DEFLATE_ERR_UNCOMP_HDR, "wrongly formatted header in uncompressed block"), \
+    A(DEFLATE_ERR_CHECKSUM, "incorrect data checksum"), \
+    A(DEFLATE_ERR_INLEN, "incorrect data length"), \
+    A(DEFLATE_ERR_UNEXPECTED_EOF, "unexpected end of data")
+#define DEFLATE_ENUM_DEF(x,y) x
+enum { DEFLATE_ERRORLIST(DEFLATE_ENUM_DEF), DEFLATE_NUM_ERRORS };
+#undef DEFLATE_ENUM_DEF
+
+/*
+ * Arrays mapping the above error codes to, respectively, a text
+ * error string and a textual representation of the symbolic error
+ * code.
+ */
+extern const char *const deflate_error_msg[DEFLATE_NUM_ERRORS];
+extern const char *const deflate_error_sym[DEFLATE_NUM_ERRORS];
+
 #endif /* DEFLATE_DEFLATE_H */