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// compressed_output.cc -- manage compressed debug sections for gold
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// Copyright 2007, 2008, 2010 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#include "parameters.h"
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#include "compressed_output.h"
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// Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE. Returns true
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// if it successfully compressed, false if it failed for any reason
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// (including not having zlib support in the library). If it returns
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// true, it allocates memory for the compressed data using new, and
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// sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
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// It also writes a header before COMPRESSED_DATA: 4 bytes saying
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// "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
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zlib_compress(const unsigned char* uncompressed_data,
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unsigned long uncompressed_size,
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unsigned char** compressed_data,
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unsigned long* compressed_size)
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const int header_size = 12;
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*compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
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*compressed_data = new unsigned char[*compressed_size + header_size];
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if (parameters->options().optimize() >= 1)
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int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
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reinterpret_cast<const Bytef*>(uncompressed_data),
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memcpy(*compressed_data, "ZLIB", 4);
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elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,
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*compressed_size += header_size;
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delete[] *compressed_data;
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*compressed_data = NULL;
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// Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer
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// UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE. Returns TRUE if it
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// decompressed successfully, false if it failed. The buffer, of
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// appropriate size, is provided by the caller, and is typically part
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// of the memory-mapped output file.
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zlib_decompress(const unsigned char* compressed_data,
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unsigned long compressed_size,
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unsigned char* uncompressed_data,
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unsigned long uncompressed_size)
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/* It is possible the section consists of several compressed
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buffers concatenated together, so we uncompress in a loop. */
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strm.avail_in = compressed_size;
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strm.next_in = const_cast<Bytef*>(compressed_data);
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strm.avail_out = uncompressed_size;
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rc = inflateInit(&strm);
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while (strm.avail_in > 0)
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strm.next_out = ((Bytef*) uncompressed_data
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+ (uncompressed_size - strm.avail_out));
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rc = inflate(&strm, Z_FINISH);
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if (rc != Z_STREAM_END)
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rc = inflateReset(&strm);
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rc = inflateEnd(&strm);
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if (rc != Z_OK || strm.avail_out != 0)
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#else // !defined(HAVE_ZLIB_H)
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zlib_compress(const unsigned char*, unsigned long,
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unsigned char**, unsigned long*)
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zlib_decompress(const unsigned char*, unsigned long,
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unsigned char*, unsigned long)
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#endif // !defined(HAVE_ZLIB_H)
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// Read the compression header of a compressed debug section and return
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// the uncompressed size.
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get_uncompressed_size(const unsigned char* compressed_data,
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section_size_type compressed_size)
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const unsigned int zlib_header_size = 12;
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/* Verify the compression header. Currently, we support only zlib
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compression, so it should be "ZLIB" followed by the uncompressed
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section size, 8 bytes in big-endian order. */
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if (compressed_size >= zlib_header_size
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&& strncmp(reinterpret_cast<const char*>(compressed_data),
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return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
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// Decompress a compressed debug section directly into the output file.
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decompress_input_section(const unsigned char* compressed_data,
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unsigned long compressed_size,
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unsigned char* uncompressed_data,
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unsigned long uncompressed_size)
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const unsigned int zlib_header_size = 12;
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/* Verify the compression header. Currently, we support only zlib
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compression, so it should be "ZLIB" followed by the uncompressed
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section size, 8 bytes in big-endian order. */
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if (compressed_size >= zlib_header_size
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&& strncmp(reinterpret_cast<const char*>(compressed_data),
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unsigned long uncompressed_size_check =
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elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
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gold_assert(uncompressed_size_check == uncompressed_size);
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return zlib_decompress(compressed_data + zlib_header_size,
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compressed_size - zlib_header_size,
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// Class Output_compressed_section.
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// Set the final data size of a compressed section. This is where
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// we actually compress the section data.
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Output_compressed_section::set_final_data_size()
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off_t uncompressed_size = this->postprocessing_buffer_size();
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// (Try to) compress the data.
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unsigned long compressed_size;
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unsigned char* uncompressed_data = this->postprocessing_buffer();
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// At this point the contents of all regular input sections will
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// have been copied into the postprocessing buffer, and relocations
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// will have been applied. Now we need to copy in the contents of
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// anything other than a regular input section.
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this->write_to_postprocessing_buffer();
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bool success = false;
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if (strcmp(this->options_->compress_debug_sections(), "zlib") == 0)
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success = zlib_compress(uncompressed_data, uncompressed_size,
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&this->data_, &compressed_size);
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// This converts .debug_foo to .zdebug_foo
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this->new_section_name_ = std::string(".z") + (this->name() + 1);
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this->set_name(this->new_section_name_.c_str());
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this->set_data_size(compressed_size);
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gold_warning(_("not compressing section data: zlib error"));
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gold_assert(this->data_ == NULL);
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this->set_data_size(uncompressed_size);
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// Write out a compressed section. If we couldn't compress, we just
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// write it out as normal, uncompressed data.
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Output_compressed_section::do_write(Output_file* of)
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off_t offset = this->offset();
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off_t data_size = this->data_size();
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unsigned char* view = of->get_output_view(offset, data_size);
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if (this->data_ == NULL)
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memcpy(view, this->postprocessing_buffer(), data_size);
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memcpy(view, this->data_, data_size);
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of->write_output_view(offset, data_size, view);
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} // End namespace gold.