New test and fixes to crcsync.

[ccan] / ccan / crcsync / crcsync.c

diff --git a/ccan/crcsync/crcsync.c b/ccan/crcsync/crcsync.c
index cb768806f6e03e829293f624ea06db540fe02e32..2301bc103c1fce4952dbb14cd88057416d62339c 100644 (file)
--- a/ccan/crcsync/crcsync.c
+++ b/ccan/crcsync/crcsync.c
@@ -138,6 +138,7 @@ size_t crc_read_block(struct crc_context *ctx, long *result,
                goto have_match;
        }
 
+       /* old is the trailing edge of the checksum window. */
        if (buffer_size(ctx) >= ctx->block_size)
                old = ctx->buffer + ctx->buffer_start;
        else
@@ -153,6 +154,7 @@ size_t crc_read_block(struct crc_context *ctx, long *result,
                                                    *old, *p,
                                                    ctx->uncrc_tab);
                        old++;
+                       /* End of stored buffer?  Start on data they gave us. */
                        if (old == ctx->buffer + ctx->buffer_end)
                                old = buf;
                } else {
@@ -167,15 +169,6 @@ size_t crc_read_block(struct crc_context *ctx, long *result,
                p++;
        }
 
-       /* Make sure we have a copy of the last block_size bytes.
-        * First, copy down the old data.  */
-       if (buffer_size(ctx)) {
-               memmove(ctx->buffer, ctx->buffer + ctx->buffer_start,
-                       buffer_size(ctx));
-               ctx->buffer_end -= ctx->buffer_start;
-               ctx->buffer_start = 0;
-       }
-
        if (crcmatch >= 0) {
                /* We have a match! */
                if (ctx->literal_bytes > ctx->block_size) {
@@ -191,18 +184,35 @@ size_t crc_read_block(struct crc_context *ctx, long *result,
                        assert(ctx->literal_bytes == 0);
                        ctx->have_match = -1;
                        ctx->running_crc = 0;
+                       /* Nothing more in the buffer. */
+                       ctx->buffer_start = ctx->buffer_end = 0;
                }
        } else {
                /* Output literal if it's more than 1 block ago. */
                if (ctx->literal_bytes > ctx->block_size) {
                        *result = ctx->literal_bytes - ctx->block_size;
-                       ctx->literal_bytes = ctx->block_size;
+                       ctx->literal_bytes -= *result;
+                       /* Advance buffer. */
+                       if (*result >= buffer_size(ctx))
+                               ctx->buffer_start = ctx->buffer_end = 0;
+                       else
+                               ctx->buffer_start += *result;
                } else
                        *result = 0;
 
                /* Now save any literal bytes we'll need in future. */
                len = ctx->literal_bytes - buffer_size(ctx);
-               memcpy(ctx->buffer + ctx->buffer_end, buf, len);
+
+               /* Move down old data if we don't have room.  */
+               if (ctx->buffer_end + len > ctx->block_size) {
+                       memmove(ctx->buffer, ctx->buffer + ctx->buffer_start,
+                               buffer_size(ctx));
+                       ctx->buffer_end -= ctx->buffer_start;
+                       ctx->buffer_start = 0;
+               }
+
+               /* Copy len bytes from tail of buffer. */
+               memcpy(ctx->buffer + ctx->buffer_end, buf + buflen - len, len);
                ctx->buffer_end += len;
                assert(buffer_size(ctx) <= ctx->block_size);
        }
@@ -239,29 +249,34 @@ static size_t final_block_match(struct crc_context *ctx)
 long crc_read_flush(struct crc_context *ctx)
 {
        long ret;
+       size_t final;
 
-       /* In case we ended on a whole block match. */
-       if (ctx->have_match == -1) {
-               size_t final;
-
-               final = final_block_match(ctx);
-               if (!final) {
-                       /* This is how many bytes we're about to consume. */
-                       ret = buffer_size(ctx);
-                       ctx->buffer_start += ret;
-                       ctx->literal_bytes -= ret;
+       /* We might have ended right on a matched block. */
+       if (ctx->have_match != -1) {
+               ctx->literal_bytes -= ctx->block_size;
+               assert(ctx->literal_bytes == 0);
+               ret = -ctx->have_match-1;
+               ctx->have_match = -1;
+               ctx->running_crc = 0;
+               /* Nothing more in the buffer. */
+               ctx->buffer_start = ctx->buffer_end;
+               return ret;
+       }
 
-                       return ret;
-               }
-               ctx->buffer_start += final;
-               ctx->literal_bytes -= final;
-               ctx->have_match = ctx->num_crcs-1;
+       /* Look for truncated final block. */
+       final = final_block_match(ctx);
+       if (!final) {
+               /* Nope?  Just a literal. */
+               ret = buffer_size(ctx);
+               ctx->buffer_start += ret;
+               ctx->literal_bytes -= ret;
+               return ret;
        }
 
-       /* It might be a partial block match, so no assert */
-       ctx->literal_bytes = 0;
-       ret = -ctx->have_match-1;
-       ctx->have_match = -1;
+       /* We matched (some of) what's left. */
+       ret = -((int)ctx->num_crcs-1)-1;
+       ctx->buffer_start += final;
+       ctx->literal_bytes -= final;
        return ret;
 }