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https://github.com/mapbox/tippecanoe.git
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75 lines
2.4 KiB
C++
75 lines
2.4 KiB
C++
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#include <string>
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#include <zlib.h>
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#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
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#include <google/protobuf/io/coded_stream.h>
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#include "protobuf.hh"
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#include "vector_tile.pb.h"
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// https://github.com/mapbox/mapnik-vector-tile/blob/master/src/vector_tile_compression.hpp
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bool is_compressed(std::string const &data) {
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return data.size() > 2 && (((uint8_t) data[0] == 0x78 && (uint8_t) data[1] == 0x9C) || ((uint8_t) data[0] == 0x1F && (uint8_t) data[1] == 0x8B));
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}
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// https://github.com/mapbox/mapnik-vector-tile/blob/master/src/vector_tile_compression.hpp
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int decompress(std::string const &input, std::string &output) {
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z_stream inflate_s;
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inflate_s.zalloc = Z_NULL;
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inflate_s.zfree = Z_NULL;
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inflate_s.opaque = Z_NULL;
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inflate_s.avail_in = 0;
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inflate_s.next_in = Z_NULL;
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if (inflateInit2(&inflate_s, 32 + 15) != Z_OK) {
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fprintf(stderr, "error: %s\n", inflate_s.msg);
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}
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inflate_s.next_in = (Bytef *) input.data();
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inflate_s.avail_in = input.size();
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size_t length = 0;
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do {
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output.resize(length + 2 * input.size());
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inflate_s.avail_out = 2 * input.size();
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inflate_s.next_out = (Bytef *) (output.data() + length);
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int ret = inflate(&inflate_s, Z_FINISH);
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if (ret != Z_STREAM_END && ret != Z_OK && ret != Z_BUF_ERROR) {
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fprintf(stderr, "error: %s\n", inflate_s.msg);
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return 0;
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}
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length += (2 * input.size() - inflate_s.avail_out);
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} while (inflate_s.avail_out == 0);
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inflateEnd(&inflate_s);
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output.resize(length);
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return 1;
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}
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// https://github.com/mapbox/mapnik-vector-tile/blob/master/src/vector_tile_compression.hpp
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int compress(std::string const &input, std::string &output) {
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z_stream deflate_s;
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deflate_s.zalloc = Z_NULL;
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deflate_s.zfree = Z_NULL;
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deflate_s.opaque = Z_NULL;
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deflate_s.avail_in = 0;
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deflate_s.next_in = Z_NULL;
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deflateInit2(&deflate_s, Z_BEST_COMPRESSION, Z_DEFLATED, 31, 8, Z_DEFAULT_STRATEGY);
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deflate_s.next_in = (Bytef *) input.data();
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deflate_s.avail_in = input.size();
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size_t length = 0;
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do {
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size_t increase = input.size() / 2 + 1024;
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output.resize(length + increase);
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deflate_s.avail_out = increase;
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deflate_s.next_out = (Bytef *) (output.data() + length);
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int ret = deflate(&deflate_s, Z_FINISH);
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if (ret != Z_STREAM_END && ret != Z_OK && ret != Z_BUF_ERROR) {
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return -1;
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}
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length += (increase - deflate_s.avail_out);
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} while (deflate_s.avail_out == 0);
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deflateEnd(&deflate_s);
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output.resize(length);
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return 0;
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}
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int dezig(unsigned n) {
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return (n >> 1) ^ (-(n & 1));
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}
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