// stringpool.h -- a string pool for gold -*- C++ -*-
+// Copyright 2006, 2007 Free Software Foundation, Inc.
+// Written by Ian Lance Taylor <iant@google.com>.
+
+// This file is part of gold.
+
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+// MA 02110-1301, USA.
+
#include <string>
#include <list>
-// Stringpool
-// Manage a pool of unique strings.
-
#ifndef GOLD_STRINGPOOL_H
#define GOLD_STRINGPOOL_H
namespace gold
{
-class Stringpool
+class Output_file;
+
+// A Stringpool is a pool of unique strings. It provides the
+// following features:
+
+// Every string in the pool is unique. Thus, if you have two strings
+// in the Stringpool, you can compare them for equality by using
+// pointer comparison rather than string comparison.
+
+// There is a key associated with every string in the pool. If you
+// add strings to the Stringpool in the same order, then the key for
+// each string will always be the same for any run of the linker.
+// This is not true of the string pointers themselves, as they may
+// change due to address space randomization. Some parts of the
+// linker (e.g., the symbol table) use the key value instead of the
+// string pointer so that repeated runs of the linker will generate
+// precisely the same output.
+
+// When you add a string to a Stringpool, Stringpool will optionally
+// make a copy of it. Thus there is no requirement to keep a copy
+// elsewhere.
+
+// A Stringpool can be turned into a string table, a sequential series
+// of null terminated strings. The first string may optionally be a
+// single zero byte, as required for SHT_STRTAB sections. This
+// conversion is only permitted after all strings have been added to
+// the Stringpool. After doing this conversion, you can ask for the
+// offset of any string in the stringpool in the string table, and you
+// can write the resulting string table to an output file.
+
+// When a Stringpool is turned into a string table, then as an
+// optimization it will reuse string suffixes to avoid duplicating
+// strings. That is, given the strings "abc" and "bc", only the
+// string "abc" will be stored, and "bc" will be represented by an
+// offset into the middle of the string "abc".
+
+// Stringpools are implemented in terms of Stringpool_template, which
+// is generalized on the type of character used for the strings. Most
+// uses will want the Stringpool type which uses char. Other cases
+// are used for merging wide string constants.
+
+template<typename Stringpool_char>
+class Stringpool_template
{
public:
- Stringpool();
+ // The type of a key into the stringpool. As described above, a key
+ // value will always be the same during any run of the linker. Zero
+ // is never a valid key value.
+ typedef size_t Key;
+
+ // Create a Stringpool.
+ Stringpool_template();
+
+ ~Stringpool_template();
+
+ // Clear all the data from the stringpool.
+ void
+ clear();
+
+ // Indicate that we should not reserve offset 0 to hold the empty
+ // string when converting the stringpool to a string table. This
+ // should not be called for a proper ELF SHT_STRTAB section.
+ void
+ set_no_zero_null()
+ { this->zero_null_ = false; }
+
+ // Add the string S to the pool. This returns a canonical permanent
+ // pointer to the string in the pool. If COPY is true, the string
+ // is copied into permanent storage. If PKEY is not NULL, this sets
+ // *PKEY to the key for the string.
+ const Stringpool_char*
+ add(const Stringpool_char* s, bool copy, Key* pkey);
- ~Stringpool();
+ // Add the prefix of length LEN of string S to the pool.
+ const Stringpool_char*
+ add_prefix(const Stringpool_char* s, size_t len, Key* pkey);
- // Add a string to the pool. This returns a canonical permanent
- // pointer to the string.
- const char* add(const char*);
+ // If the string S is present in the pool, return the canonical
+ // string pointer. Otherwise, return NULL. If PKEY is not NULL,
+ // set *PKEY to the key.
+ const Stringpool_char*
+ find(const Stringpool_char* s, Key* pkey) const;
- const char* add(const std::string& s)
- { return this->add(s.c_str()); }
+ // Turn the stringpool into a string table: determine the offsets of
+ // all the strings. After this is called, no more strings may be
+ // added to the stringpool.
+ void
+ set_string_offsets();
- // Add the prefix of a string to the pool.
- const char* add(const char *, size_t);
+ // Get the offset of the string S in the string table. This returns
+ // the offset in bytes, not in units of Stringpool_char. This may
+ // only be called after set_string_offsets has been called.
+ off_t
+ get_offset(const Stringpool_char* s) const;
+
+ // Get the offset of the string S in the string table.
+ off_t
+ get_offset(const std::basic_string<Stringpool_char>& s) const
+ { return this->get_offset(s.c_str()); }
+
+ // Get the size of the string table. This returns the number of
+ // bytes, not in units of Stringpool_char.
+ off_t
+ get_strtab_size() const
+ {
+ gold_assert(this->strtab_size_ != 0);
+ return this->strtab_size_;
+ }
+
+ // Write the string table into the output file at the specified
+ // offset.
+ void
+ write(Output_file*, off_t offset);
+
+ // Write the string table into the specified buffer, of the
+ // specified size. buffer_size should be at least
+ // get_strtab_size().
+ void
+ write_to_buffer(unsigned char* buffer, size_t buffer_size);
+
+ // Dump statistical information to stderr.
+ void
+ print_stats(const char*) const;
private:
- Stringpool(const Stringpool&);
- Stringpool& operator=(const Stringpool&);
+ Stringpool_template(const Stringpool_template&);
+ Stringpool_template& operator=(const Stringpool_template&);
+
+ // Return the length of a string in units of Stringpool_char.
+ static size_t
+ string_length(const Stringpool_char*);
- struct stringdata
+ // We store the actual data in a list of these buffers.
+ struct Stringdata
{
// Length of data in buffer.
size_t len;
// Allocated size of buffer.
size_t alc;
+ // Buffer index.
+ unsigned int index;
// Buffer.
char data[1];
};
- const char* add_string(const char*);
+ // Copy a string into the buffers, returning a canonical string.
+ const Stringpool_char*
+ add_string(const Stringpool_char*, Key*);
+ // Hash function.
struct Stringpool_hash
{
size_t
- operator()(const char*) const;
+ operator()(const Stringpool_char*) const;
};
+ // Equality comparison function for hash table.
struct Stringpool_eq
{
bool
- operator()(const char* p1, const char* p2) const
- { return strcmp(p1, p2) == 0; }
+ operator()(const Stringpool_char* p1, const Stringpool_char* p2) const;
};
+ // Return whether s1 is a suffix of s2.
+ static bool
+ is_suffix(const Stringpool_char* s1, size_t len1,
+ const Stringpool_char* s2, size_t len2);
+
+ // The hash table is a map from string names to a pair of Key and
+ // string table offsets. We only use the offsets if we turn this
+ // into an string table section.
+
+ typedef std::pair<Key, off_t> Val;
+
#ifdef HAVE_TR1_UNORDERED_SET
- typedef Unordered_set<const char*, Stringpool_hash, Stringpool_eq,
- std::allocator<const char*>,
+ typedef Unordered_map<const Stringpool_char*, Val, Stringpool_hash,
+ Stringpool_eq,
+ std::allocator<std::pair<const Stringpool_char* const,
+ Val> >,
true> String_set_type;
#else
- typedef Unordered_set<const char*, Stringpool_hash, Stringpool_eq,
- std::allocator<const char*> > String_set_type;
+ typedef Unordered_map<const Stringpool_char*, Val, Stringpool_hash,
+ Stringpool_eq> String_set_type;
#endif
+ // Comparison routine used when sorting into a string table. We
+ // store string-sizes in the sort-vector so we don't have to
+ // recompute them log(n) times as we sort.
+ struct Stringpool_sort_info
+ {
+ typename String_set_type::iterator it;
+ size_t string_length;
+ Stringpool_sort_info(typename String_set_type::iterator i, size_t s)
+ : it(i), string_length(s)
+ { }
+ };
+
+ struct Stringpool_sort_comparison
+ {
+ bool
+ operator()(const Stringpool_sort_info&, const Stringpool_sort_info&) const;
+ };
+
+ // List of Stringdata structures.
+ typedef std::list<Stringdata*> Stringdata_list;
+
+ // Mapping from const char* to namepool entry.
String_set_type string_set_;
- std::list<stringdata*> strings_;
+ // List of buffers.
+ Stringdata_list strings_;
+ // Size of string table.
+ off_t strtab_size_;
+ // Next Stringdata index.
+ unsigned int next_index_;
+ // Next key value for a string we don't copy.
+ int next_uncopied_key_;
+ // Whether to reserve offset 0 to hold the null string.
+ bool zero_null_;
};
+// The most common type of Stringpool.
+typedef Stringpool_template<char> Stringpool;
+
} // End namespace gold.
#endif // !defined(GOLD_STRINGPOOL_H)
projects / deliverable / binutils-gdb.git / blobdiff