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extractExternal.cpp
/*
* extractExternal.cpp
*/
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include <fstream>
#include <iostream>
#include <map>
#include <set>
#include <stdlib.h>
#include <string>
#include <strstream>
/* Given a set of n object files h ('external' object files) and a set of m
object files o ('internal' object files),
1. Determines r, the subset of h that o depends on, directly or indirectly
2. Removes the files in h - r from the file system
3. For each external symbol defined in some file in r, rename it in r U o
by prefixing it with "__kmp_external_"
Usage:
hide.exe <n> <filenames for h> <filenames for o>
Thus, the prefixed symbols become hidden in the sense that they now have a
special prefix.
*/
using namespace std;
void stop(char *errorMsg) {
printf("%s\n", errorMsg);
exit(1);
}
// an entry in the symbol table of a .OBJ file
class Symbol {
public:
__int64 name;
unsigned value;
unsigned short sectionNum, type;
char storageClass, nAux;
};
class _rstream : public istrstream {
private:
const char *buf;
protected:
_rstream(pair<const char *, streamsize> p)
: istrstream(p.first, p.second), buf(p.first) {}
~_rstream() { delete[] buf; }
};
// A stream encapsulating the content of a file or the content of a string,
// overriding the >> operator to read various integer types in binary form,
// as well as a symbol table entry.
class rstream : public _rstream {
private:
template <class T> inline rstream &doRead(T &x) {
read((char *)&x, sizeof(T));
return *this;
}
static pair<const char *, streamsize> getBuf(const char *fileName) {
ifstream raw(fileName, ios::binary | ios::in);
if (!raw.is_open())
stop("rstream.getBuf: Error opening file");
raw.seekg(0, ios::end);
streampos fileSize = raw.tellg();
if (fileSize < 0)
stop("rstream.getBuf: Error reading file");
char *buf = new char[fileSize];
raw.seekg(0, ios::beg);
raw.read(buf, fileSize);
return pair<const char *, streamsize>(buf, fileSize);
}
public:
// construct from a string
rstream(const char *buf, streamsize size)
: _rstream(pair<const char *, streamsize>(buf, size)) {}
// construct from a file whole content is fully read once to initialize the
// content of this stream
rstream(const char *fileName) : _rstream(getBuf(fileName)) {}
rstream &operator>>(int &x) { return doRead(x); }
rstream &operator>>(unsigned &x) { return doRead(x); }
rstream &operator>>(short &x) { return doRead(x); }
rstream &operator>>(unsigned short &x) { return doRead(x); }
rstream &operator>>(Symbol &e) {
read((char *)&e, 18);
return *this;
}
};
// string table in a .OBJ file
class StringTable {
private:
map<string, unsigned> directory;
size_t length;
char *data;
// make <directory> from <length> bytes in <data>
void makeDirectory(void) {
unsigned i = 4;
while (i < length) {
string s = string(data + i);
directory.insert(make_pair(s, i));
i += s.size() + 1;
}
}
// initialize <length> and <data> with contents specified by the arguments
void init(const char *_data) {
unsigned _length = *(unsigned *)_data;
if (_length < sizeof(unsigned) || _length != *(unsigned *)_data)
stop("StringTable.init: Invalid symbol table");
if (_data[_length - 1]) {
// to prevent runaway strings, make sure the data ends with a zero
data = new char[length = _length + 1];
data[_length] = 0;
} else {
data = new char[length = _length];
}
*(unsigned *)data = length;
KMP_MEMCPY(data + sizeof(unsigned), _data + sizeof(unsigned),
length - sizeof(unsigned));
makeDirectory();
}
public:
StringTable(rstream &f) {
// Construct string table by reading from f.
streampos s;
unsigned strSize;
char *strData;
s = f.tellg();
f >> strSize;
if (strSize < sizeof(unsigned))
stop("StringTable: Invalid string table");
strData = new char[strSize];
*(unsigned *)strData = strSize;
// read the raw data into <strData>
f.read(strData + sizeof(unsigned), strSize - sizeof(unsigned));
s = f.tellg() - s;
if (s < strSize)
stop("StringTable: Unexpected EOF");
init(strData);
delete[] strData;
}
StringTable(const set<string> &strings) {
// Construct string table from given strings.
char *p;
set<string>::const_iterator it;
size_t s;
// count required size for data
for (length = sizeof(unsigned), it = strings.begin(); it != strings.end();
++it) {
size_t l = (*it).size();
if (l > (unsigned)0xFFFFFFFF)
stop("StringTable: String too long");
if (l > 8) {
length += l + 1;
if (length > (unsigned)0xFFFFFFFF)
stop("StringTable: Symbol table too long");
}
}
data = new char[length];
*(unsigned *)data = length;
// populate data and directory
for (p = data + sizeof(unsigned), it = strings.begin(); it != strings.end();
++it) {
const string &str = *it;
size_t l = str.size();
if (l > 8) {
directory.insert(make_pair(str, p - data));
KMP_MEMCPY(p, str.c_str(), l);
p[l] = 0;
p += l + 1;
}
}
}
~StringTable() { delete[] data; }
// Returns encoding for given string based on this string table. Error if
// string length is greater than 8 but string is not in the string table
// -- returns 0.
__int64 encode(const string &str) {
__int64 r;
if (str.size() <= 8) {
// encoded directly
((char *)&r)[7] = 0;
KMP_STRNCPY_S((char *)&r, sizeof(r), str.c_str(), 8);
return r;
} else {
// represented as index into table
map<string, unsigned>::const_iterator it = directory.find(str);
if (it == directory.end())
stop("StringTable::encode: String now found in string table");
((unsigned *)&r)[0] = 0;
((unsigned *)&r)[1] = (*it).second;
return r;
}
}
// Returns string represented by x based on this string table. Error if x
// references an invalid position in the table--returns the empty string.
string decode(__int64 x) const {
if (*(unsigned *)&x == 0) {
// represented as index into table
unsigned &p = ((unsigned *)&x)[1];
if (p >= length)
stop("StringTable::decode: Invalid string table lookup");
return string(data + p);
} else {
// encoded directly
char *p = (char *)&x;
int i;
for (i = 0; i < 8 && p[i]; ++i)
;
return string(p, i);
}
}
void write(ostream &os) { os.write(data, length); }
};
// for the named object file, determines the set of defined symbols and the set
// of undefined external symbols and writes them to <defined> and <undefined>
// respectively
void computeExternalSymbols(const char *fileName, set<string> *defined,
set<string> *undefined) {
streampos fileSize;
size_t strTabStart;
unsigned symTabStart, symNEntries;
rstream f(fileName);
f.seekg(0, ios::end);
fileSize = f.tellg();
f.seekg(8);
f >> symTabStart >> symNEntries;
// seek to the string table
f.seekg(strTabStart = symTabStart + 18 * (size_t)symNEntries);
if (f.eof()) {
printf("computeExternalSymbols: fileName='%s', fileSize = %lu, symTabStart "
"= %u, symNEntries = %u\n",
fileName, (unsigned long)fileSize, symTabStart, symNEntries);
stop("computeExternalSymbols: Unexpected EOF 1");
}
StringTable stringTable(f); // read the string table
if (f.tellg() != fileSize)
stop("computeExternalSymbols: Unexpected data after string table");
f.clear();
f.seekg(symTabStart); // seek to the symbol table
defined->clear();
undefined->clear();
for (int i = 0; i < symNEntries; ++i) {
// process each entry
Symbol e;
if (f.eof())
stop("computeExternalSymbols: Unexpected EOF 2");
f >> e;
if (f.fail())
stop("computeExternalSymbols: File read error");
if (e.nAux) { // auxiliary entry: skip
f.seekg(e.nAux * 18, ios::cur);
i += e.nAux;
}
// if symbol is extern and defined in the current file, insert it
if (e.storageClass == 2)
if (e.sectionNum)
defined->insert(stringTable.decode(e.name));
else
undefined->insert(stringTable.decode(e.name));
}
}
// For each occurrence of an external symbol in the object file named by
// by <fileName> that is a member of <hide>, renames it by prefixing
// with "__kmp_external_", writing back the file in-place
void hideSymbols(char *fileName, const set<string> &hide) {
static const string prefix("__kmp_external_");
set<string> strings; // set of all occurring symbols, appropriately prefixed
streampos fileSize;
size_t strTabStart;
unsigned symTabStart, symNEntries;
int i;
rstream in(fileName);
in.seekg(0, ios::end);
fileSize = in.tellg();
in.seekg(8);
in >> symTabStart >> symNEntries;
in.seekg(strTabStart = symTabStart + 18 * (size_t)symNEntries);
if (in.eof())
stop("hideSymbols: Unexpected EOF");
StringTable stringTableOld(in); // read original string table
if (in.tellg() != fileSize)
stop("hideSymbols: Unexpected data after string table");
// compute set of occurring strings with prefix added
for (i = 0; i < symNEntries; ++i) {
Symbol e;
in.seekg(symTabStart + i * 18);
if (in.eof())
stop("hideSymbols: Unexpected EOF");
in >> e;
if (in.fail())
stop("hideSymbols: File read error");
if (e.nAux)
i += e.nAux;
const string &s = stringTableOld.decode(e.name);
// if symbol is extern and found in <hide>, prefix and insert into strings,
// otherwise, just insert into strings without prefix
strings.insert(
(e.storageClass == 2 && hide.find(s) != hide.end()) ? prefix + s : s);
}
ofstream out(fileName, ios::trunc | ios::out | ios::binary);
if (!out.is_open())
stop("hideSymbols: Error opening output file");
// make new string table from string set
StringTable stringTableNew = StringTable(strings);
// copy input file to output file up to just before the symbol table
in.seekg(0);
char *buf = new char[symTabStart];
in.read(buf, symTabStart);
out.write(buf, symTabStart);
delete[] buf;
// copy input symbol table to output symbol table with name translation
for (i = 0; i < symNEntries; ++i) {
Symbol e;
in.seekg(symTabStart + i * 18);
if (in.eof())
stop("hideSymbols: Unexpected EOF");
in >> e;
if (in.fail())
stop("hideSymbols: File read error");
const string &s = stringTableOld.decode(e.name);
out.seekp(symTabStart + i * 18);
e.name = stringTableNew.encode(
(e.storageClass == 2 && hide.find(s) != hide.end()) ? prefix + s : s);
out.write((char *)&e, 18);
if (out.fail())
stop("hideSymbols: File write error");
if (e.nAux) {
// copy auxiliary symbol table entries
int nAux = e.nAux;
for (int j = 1; j <= nAux; ++j) {
in >> e;
out.seekp(symTabStart + (i + j) * 18);
out.write((char *)&e, 18);
}
i += nAux;
}
}
// output string table
stringTableNew.write(out);
}
// returns true iff <a> and <b> have no common element
template <class T> bool isDisjoint(const set<T> &a, const set<T> &b) {
set<T>::const_iterator ita, itb;
for (ita = a.begin(), itb = b.begin(); ita != a.end() && itb != b.end();) {
const T &ta = *ita, &tb = *itb;
if (ta < tb)
++ita;
else if (tb < ta)
++itb;
else
return false;
}
return true;
}
// PRE: <defined> and <undefined> are arrays with <nTotal> elements where
// <nTotal> >= <nExternal>. The first <nExternal> elements correspond to the
// external object files and the rest correspond to the internal object files.
// POST: file x is said to depend on file y if undefined[x] and defined[y] are
// not disjoint. Returns the transitive closure of the set of internal object
// files, as a set of file indexes, under the 'depends on' relation, minus the
// set of internal object files.
set<int> *findRequiredExternal(int nExternal, int nTotal, set<string> *defined,
set<string> *undefined) {
set<int> *required = new set<int>;
set<int> fresh[2];
int i, cur = 0;
bool changed;
for (i = nTotal - 1; i >= nExternal; --i)
fresh[cur].insert(i);
do {
changed = false;
for (set<int>::iterator it = fresh[cur].begin(); it != fresh[cur].end();
++it) {
set<string> &s = undefined[*it];
for (i = 0; i < nExternal; ++i) {
if (required->find(i) == required->end()) {
if (!isDisjoint(defined[i], s)) {
// found a new qualifying element
required->insert(i);
fresh[1 - cur].insert(i);
changed = true;
}
}
}
}
fresh[cur].clear();
cur = 1 - cur;
} while (changed);
return required;
}
int main(int argc, char **argv) {
int nExternal, nInternal, i;
set<string> *defined, *undefined;
set<int>::iterator it;
if (argc < 3)
stop("Please specify a positive integer followed by a list of object "
"filenames");
nExternal = atoi(argv[1]);
if (nExternal <= 0)
stop("Please specify a positive integer followed by a list of object "
"filenames");
if (nExternal + 2 > argc)
stop("Too few external objects");
nInternal = argc - nExternal - 2;
defined = new set<string>[argc - 2];
undefined = new set<string>[argc - 2];
// determine the set of defined and undefined external symbols
for (i = 2; i < argc; ++i)
computeExternalSymbols(argv[i], defined + i - 2, undefined + i - 2);
// determine the set of required external files
set<int> *requiredExternal =
findRequiredExternal(nExternal, argc - 2, defined, undefined);
set<string> hide;
// determine the set of symbols to hide--namely defined external symbols of
// the required external files
for (it = requiredExternal->begin(); it != requiredExternal->end(); ++it) {
int idx = *it;
set<string>::iterator it2;
// We have to insert one element at a time instead of inserting a range
// because the insert member function taking a range doesn't exist on
// Windows* OS, at least at the time of this writing.
for (it2 = defined[idx].begin(); it2 != defined[idx].end(); ++it2)
hide.insert(*it2);
}
// process the external files--removing those that are not required and hiding
// the appropriate symbols in the others
for (i = 0; i < nExternal; ++i)
if (requiredExternal->find(i) != requiredExternal->end())
hideSymbols(argv[2 + i], hide);
else
remove(argv[2 + i]);
// hide the appropriate symbols in the internal files
for (i = nExternal + 2; i < argc; ++i)
hideSymbols(argv[i], hide);
return 0;
}