/* packed_data.h : Interface to the packed binary stream data structure * * ==================================================================== * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. * ==================================================================== */ #ifndef SVN_PACKED_DATA_H #define SVN_PACKED_DATA_H #include "svn_string.h" #include "svn_io.h" #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ /* This API provides Yet Another Serialization Framework. * * It is geared towards efficiently encoding collections of structured * binary data (e.g. an array of noderev objects). The basic idea is to * transform them into hierarchies of streams with each stream usually * corresponding to a single attribute in the original data structures. * The user is free model the mapping structure <-> streams mapping as she * sees fit. * * With all data inside the same (sub-)stream carrying similar attribute * values, the whole stream lends itself to data compression. Strings / * plain byte sequences will be stored as is. Numbers use a 7b/8b encoding * scheme to eliminate leading zeros. Because values are often dependent * (increasing offsets, roughly similar revision number, etc.), streams * can be configured as storing (hopefully shorter) deltas instead of the * original value. * * Two stream types are provided: integer and byte streams. While the * first store 64 bit integers only and can be configured to assume * signed and / or deltifyable data, the second will store arbitrary * byte sequences including their length. At the root level, you may * create an arbitrary number of integer and byte streams. Any stream * may have an arbitrary number of sub-streams of the same kind. You * should create the full stream hierarchy before writing any data to it. * * As a convenience, when an integer stream has sub-streams, you may write * to the parent stream instead of all sub-streams individually and the * values will be passed down automatically in a round-robin fashion. * Reading from the parent stream is similarly supported. * * When all data has been added to the stream, it can be written to an * ordinary svn_stream_t. First, we write a description of the stream * structure (types, sub-streams, sizes and configurations) followed by * zlib compressed stream content. For each top-level stream, all sub- * stream data will be concatenated and then compressed as a single block. * To maximize the effect of this, make sure all data in that stream * hierarchy has a similar value distribution. * * Reading data starts with an svn_stream_t and automatically recreates * the stream hierarchies. You only need to extract data from it in the * same order as you wrote it. * * Although not enforced programmatically, you may either only write to a * stream hierarchy or only read from it but you cannot do both on the * same data structure. */ /* We pack / unpack integers en block to minimize calling and setup overhead. * This is the number of integers we put into a buffer before writing them * them to / after reading them from the 7b/8b stream. Under 64 bits, this * value creates a 128 byte data structure (14 + 2 integers, 8 bytes each). */ #define SVN__PACKED_DATA_BUFFER_SIZE 14 /* Data types. */ /* Opaque type for the root object. */ typedef struct svn_packed__data_root_t svn_packed__data_root_t; /* Opaque type for byte streams. */ typedef struct svn_packed__byte_stream_t svn_packed__byte_stream_t; /* Semi-opaque type for integer streams. We expose the unpacked buffer * to allow for replacing svn_packed__add_uint and friends by macros. */ typedef struct svn_packed__int_stream_t { /* pointer to the remainder of the data structure */ void *private_data; /* number of value entries in BUFFER */ apr_size_t buffer_used; /* unpacked integers (either yet to be packed or pre-fetched from the * packed buffers). Only the first BUFFER_USED entries are valid. */ apr_uint64_t buffer[SVN__PACKED_DATA_BUFFER_SIZE]; } svn_packed__int_stream_t; /* Writing data. */ /* Return a new serialization root object, allocated in POOL. */ svn_packed__data_root_t * svn_packed__data_create_root(apr_pool_t *pool); /* Create and return a new top-level integer stream in ROOT. If signed, * negative numbers will be put into that stream, SIGNED_INTS should be * TRUE as a more efficient encoding will be used in that case. Set * DIFF to TRUE if you expect the difference between consecutive numbers * to be much smaller (~100 times) than the actual numbers. */ svn_packed__int_stream_t * svn_packed__create_int_stream(svn_packed__data_root_t *root, svn_boolean_t diff, svn_boolean_t signed_ints); /* Create and return a sub-stream to the existing integer stream PARENT. * If signed, negative numbers will be put into that stream, SIGNED_INTS * should be TRUE as a more efficient encoding will be used in that case. * Set DIFF to TRUE if you expect the difference between consecutive numbers * to be much smaller (~100 times) than the actual numbers. */ svn_packed__int_stream_t * svn_packed__create_int_substream(svn_packed__int_stream_t *parent, svn_boolean_t diff, svn_boolean_t signed_ints); /* Create and return a new top-level byte sequence stream in ROOT. */ svn_packed__byte_stream_t * svn_packed__create_bytes_stream(svn_packed__data_root_t *root); /* Write the unsigned integer VALUE to STEAM. */ void svn_packed__add_uint(svn_packed__int_stream_t *stream, apr_uint64_t value); /* Write the signed integer VALUE to STEAM. */ void svn_packed__add_int(svn_packed__int_stream_t *stream, apr_int64_t value); /* Write the sequence stating at DATA containing LEN bytes to STEAM. */ void svn_packed__add_bytes(svn_packed__byte_stream_t *stream, const char *data, apr_size_t len); /* Write all contents of ROOT (including all sub-streams) to STREAM. * Use SCRATCH_POOL for temporary allocations. */ svn_error_t * svn_packed__data_write(svn_stream_t *stream, svn_packed__data_root_t *root, apr_pool_t *scratch_pool); /* Reading data. */ /* Return the first integer stream in ROOT. Returns NULL in case there * aren't any. */ svn_packed__int_stream_t * svn_packed__first_int_stream(svn_packed__data_root_t *root); /* Return the first byte sequence stream in ROOT. Returns NULL in case * there aren't any. */ svn_packed__byte_stream_t * svn_packed__first_byte_stream(svn_packed__data_root_t *root); /* Return the next (sibling) integer stream to STREAM. Returns NULL in * case there isn't any. */ svn_packed__int_stream_t * svn_packed__next_int_stream(svn_packed__int_stream_t *stream); /* Return the next (sibling) byte sequence stream to STREAM. Returns NULL * in case there isn't any. */ svn_packed__byte_stream_t * svn_packed__next_byte_stream(svn_packed__byte_stream_t *stream); /* Return the first sub-stream of STREAM. Returns NULL in case there * isn't any. */ svn_packed__int_stream_t * svn_packed__first_int_substream(svn_packed__int_stream_t *stream); /* Return the number of integers left to read from STREAM. */ apr_size_t svn_packed__int_count(svn_packed__int_stream_t *stream); /* Return the number of bytes left to read from STREAM. */ apr_size_t svn_packed__byte_count(svn_packed__byte_stream_t *stream); /* Return the next number from STREAM as unsigned integer. Returns 0 when * reading beyond the end of the stream. */ apr_uint64_t svn_packed__get_uint(svn_packed__int_stream_t *stream); /* Return the next number from STREAM as signed integer. Returns 0 when * reading beyond the end of the stream. */ apr_int64_t svn_packed__get_int(svn_packed__int_stream_t *stream); /* Return the next byte sequence from STREAM and set *LEN to the length * of that sequence. Sets *LEN to 0 when reading beyond the end of the * stream. */ const char * svn_packed__get_bytes(svn_packed__byte_stream_t *stream, apr_size_t *len); /* Allocate a new packed data root in RESULT_POOL, read its structure and * stream contents from STREAM and return it in *ROOT_P. Use SCRATCH_POOL * for temporary allocations. */ svn_error_t * svn_packed__data_read(svn_packed__data_root_t **root_p, svn_stream_t *stream, apr_pool_t *result_pool, apr_pool_t *scratch_pool); #ifdef __cplusplus } #endif /* __cplusplus */ #endif /* SVN_PACKED_DATA_H */