Add block processor data structure

The interface is designed for parallel, asynchronuous processing of data
blocks with an I/O callback that handles the serialized result.

The underlying implementation is currently still synchronuous.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 111 insertions, 0 deletions

diff --git a/include/block_processor.h b/include/block_processor.h
new file mode 100644
index 0000000..4944969
--- /dev/null
+++ b/include/block_processor.h
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * block_processor.h
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#ifndef BLOCK_PROCESSOR_H
+#define BLOCK_PROCESSOR_H
+
+#include "config.h"
+#include "compress.h"
+
+enum {
+	/* only calculate checksum, do NOT compress the data */
+	BLK_DONT_COMPRESS = 0x0001,
+
+	/* set by compressor worker if the block was actually compressed */
+	BLK_IS_COMPRESSED = 0x0002,
+
+	/* do not calculate block checksum */
+	BLK_DONT_CHECKSUM = 0x0004,
+
+	/* set by compressor worker if compression failed */
+	BLK_COMPRESS_ERROR = 0x0008,
+
+	/* first user setable block flag */
+	BLK_USER = 0x0080
+};
+
+typedef struct block_t {
+	/* used internally, ignored and overwritten when enqueueing blocks */
+	struct block_t *next;
+	uint32_t sequence_number;
+
+	/* Size of the data area */
+	uint32_t size;
+
+	/* checksum of the input data */
+	uint32_t checksum;
+
+	/* user settable file block index */
+	uint32_t index;
+
+	/* user pointer associated with the block */
+	void *user;
+
+	/* user settable flag field */
+	uint32_t flags;
+
+	/* raw data to be processed */
+	uint8_t data[];
+} block_t;
+
+typedef struct block_processor_t block_processor_t;
+
+/*
+  Gets called for each processed block. May be called from a different thread
+  than the one that calls enqueue, but only from one thread at a time.
+  Guaranteed to be called on blocks in the order that they are submitted
+  to enqueue.
+
+  A non-zero return value is interpreted as fatal error.
+ */
+typedef int (*block_cb)(void *user, block_t *blk);
+
+block_processor_t *block_processor_create(size_t max_block_size,
+					  compressor_t *cmp,
+					  unsigned int num_workers,
+					  void *user,
+					  block_cb callback);
+
+void block_processor_destroy(block_processor_t *proc);
+
+/*
+  Add a block to be processed. Returns non-zero on error and prints a message
+  to stderr.
+
+  The function takes over ownership of the submitted block. It is freed with
+  a after processing and calling the block callback.
+
+  Even on failure, the workers may still be running and
+  block_processor_finish must be called before cleaning up.
+*/
+int block_processor_enqueue(block_processor_t *proc, block_t *block);
+
+/*
+  Wait for the compressor workers to finish. Returns zero on success, non-zero
+  if an internal error occoured or one of the block callbacks returned a
+  non-zero value.
+ */
+int block_processor_finish(block_processor_t *proc);
+
+/*
+  Convenience function to create a block structure and optionally fill it with
+  content.
+
+  filename is used for printing error messages. If fd is a valid file
+  descriptor (>= 0), the function attempts to populate the payload data
+  from the input file.
+ */
+block_t *create_block(const char *filename, int fd, size_t size,
+		      void *user, uint32_t flags);
+
+/*
+  Convenience function to process a data block. Returns 0 on success,
+  prints to stderr on failure.
+ */
+int process_block(block_t *block, compressor_t *cmp,
+		  uint8_t *scratch, size_t scratch_size);
+
+#endif /* BLOCK_PROCESSOR_H */