/*
 * extractExternal.cpp
 * $Revision: 42181 $
 * $Date: 2013-03-26 15:04:45 -0500 (Tue, 26 Mar 2013) $
 */


//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.txt for details.
//
//===----------------------------------------------------------------------===//


#include <stdlib.h>
#include <iostream>
#include <strstream>
#include <fstream>
#include <string>
#include <set>
#include <map>

/* 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 encapuslating 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;
	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));
		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;
	    strncpy((char*)&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;
}

/* precondition: <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.
   postcondition: 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;
}
