crc sync module.

[ccan] / ccan / crcsync / crcsync.h

diff --git a/ccan/crcsync/crcsync.h b/ccan/crcsync/crcsync.h
new file mode 100644 (file)
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+++ b/ccan/crcsync/crcsync.h
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+#ifndef CCAN_CRCSYNC_H
+#define CCAN_CRCSYNC_H
+#include <stdint.h>
+#include <stddef.h>
+
+/**
+ * crc_of_blocks - calculate the crc of the blocks.
+ * @data: pointer to the buffer to CRC
+ * @len: length of the buffer
+ * @blocksize: CRC of each block (final block may be shorter)
+ * @crcbits: the number of bits of crc you want (currently 32 maximum)
+ * @crc: the crcs (array will have (len + blocksize-1)/blocksize entries).
+ *
+ * Calculates the CRC of each block, and output the lower @crcbits to
+ * @crc array.
+ */
+void crc_of_blocks(const void *data, size_t len, unsigned int blocksize,
+                  unsigned int crcbits, uint32_t crc[]);
+
+/**
+ * crc_context_new - allocate and initialize state for crc_find_block
+ * @blocksize: the sie of each block
+ * @crcbits: the bits valid in the CRCs (<= 32)
+ * @crc: array of block crcs
+ * @num_crcs: number of block crcs
+ *
+ * Returns an allocated pointer to the structure for crc_find_block,
+ * or NULL.  Makes a copy of @crc and @num_crcs.
+ */
+struct crc_context *crc_context_new(size_t blocksize, unsigned crcbits,
+                                   const uint32_t crc[], unsigned num_crcs);
+
+/**
+ * crc_read_block - search for block matches in the buffer.
+ * @ctx: struct crc_context from crc_context_new.
+ * @result: unmatched bytecount, or crc which matched.
+ * @buf: pointer to bytes
+ * @buflen: length of buffer
+ *
+ * Returns the number of bytes of the buffer which have been digested,
+ * and sets @result either to a negagive number (== -crc_number - 1)
+ * to show that a block matched a crc, or zero or more to represent a
+ * length of unmatched data.
+ *
+ * Note that multiple lengths of unmatched data might be returned in a row:
+ * you'll probably want to merge them yourself.
+ */
+size_t crc_read_block(struct crc_context *ctx, long *result,
+                     const void *buf, size_t buflen);
+
+/**
+ * crc_read_flush - flush any remaining data from crc_read_block.
+ * @ctx: the context passed to crc_read_block.
+ *
+ * Matches the final data.  This can be used to create a boundary, or
+ * simply flush the final data.  Keep calling it until it returns 0.
+ */
+long crc_read_flush(struct crc_context *ctx);
+
+/**
+ * crc_context_free - free a context returned from crc_context_new.
+ * @ctx: the context returned from crc_context_new, or NULL.
+ */
+void crc_context_free(struct crc_context *ctx);
+
+#endif /* CCAN_CRCSYNC_H */