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#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <string.h>
#include <lua.h>
#include <lauxlib.h>
#define CKE(val, name) do { if (val == -1) { perror(name); exit(1); } } while (0)
static inline void *CKN(void *p) { if (p == NULL) { fprintf(stderr,"out of memory!"); exit(1); } return p; }
#ifdef DEBUG
#define DP(...) fprintf(stderr, __VA_ARGS__);
#else
#define DP(...)
#endif
int filefork(char *argv[], int input, int output) {
int pid = fork();
switch (pid) {
case -1: perror("fork"); exit(1); break;
case 0:
if (input != -1) {
CKE(close(STDIN_FILENO),"close stdin");
CKE(dup2(input, STDIN_FILENO),"dup2 stdin");
}
if (output != -1) {
CKE(close(STDOUT_FILENO),"close stdout");
CKE(dup2(output, STDOUT_FILENO),"dup2 stdout");
}
CKE(execvp(argv[0], argv), "exec");
exit(1);
break;
default: return pid;
}
}
int echofork(char *str, size_t len, int fd) {
int pid = fork();
switch (pid) {
case -1: perror("fork"), exit(1); break;
case 0:
size_t remaining = len;
char *cur = str;
do {
ssize_t res = write(fd, cur, remaining);
if (res == -1) { perror("write"); exit(1); }
cur += res;
remaining -= res;
} while (remaining > 0);
exit(0);
default: return pid;
}
}
void empipe(int pipefd[2]) {
CKE(pipe(pipefd), "pipe");
fcntl(pipefd[0], F_SETFD, FD_CLOEXEC);
fcntl(pipefd[1], F_SETFD, FD_CLOEXEC);
}
char *run(int count, char **progs[], size_t inputlen, char *inputstr, size_t *outlen) {
if (inputstr) count++;
int (*pipefds)[2] = CKN(malloc(count * sizeof(int[2])));
pid_t *pids = CKN(malloc(count * sizeof(pid_t)));
for (int i = 0; i < count; i++) empipe(pipefds[i]);
for (int i = 0; i < count; i++) {
int input = (i == 0) ? -1 : pipefds[i-1][0];
int output = pipefds[i][1];
if (!inputstr) pids[i] = filefork(progs[i ], input, output);
else if (i==0) pids[i] = echofork(inputstr, inputlen, output);
else pids[i] = filefork(progs[i-1], input, output);
DP("[%d] %d\n",i,pids[i]);
}
// pipes need to be closed everywhere they aren't being used.
// close them in the parent process here; CLOEXEC will take care of them everwhere else
// (duped fds won't have CLOEXEC set so those ones, ie the ones being used, won't be closed)
for (int i = 0; i < count-1; i++) {
CKE(close(pipefds[i][0]), "close");
CKE(close(pipefds[i][1]), "close");
}
CKE(close(pipefds[count-1][1]), "close");
// if the program produces too much data, you will be killed
size_t readed = 0;
size_t cap = 2048;
char *buf = CKN(malloc(cap*sizeof(char)));
size_t remaining = cap;
size_t amt = 0;
do {
amt = read(pipefds[count-1][0], buf+readed, remaining);
readed += amt;
remaining -= amt;
if (remaining == 0) {
buf = CKN(realloc(buf, cap + cap));
remaining += cap;
cap += cap;
}
} while (amt != 0);
CKE(close(pipefds[count-1][0]), "close");
for (int i = 0; i < count; i++) {
int status;
pid_t rpid = waitpid(pids[i], &status, 0);
DP("-> %d %d\n",rpid,WEXITSTATUS(status));
}
free(pipefds);
free(pids);
*outlen = readed;
return buf;
}
#define FAIL(msg) do { luaL_where(L, 1); lua_pushliteral(L, msg); lua_concat(L, 2); fail = 1; goto finish; } while (0)
int do_the_thing(lua_State *L) {
int fail = 0;
char ***argvs = NULL;
char *outbuf = NULL;
size_t nprogs = 0;
if (lua_gettop(L) != 1) FAIL("run wants exactly one argument");
if (lua_type(L, 1) != LUA_TTABLE) FAIL("run needs table argumnt");
nprogs = lua_rawlen(L, 1);
if (nprogs == 0) FAIL("need at least one program to run");
argvs = CKN(calloc(nprogs, sizeof(char**)));
for (int i = 0; i < nprogs; i++) {
int ty = lua_rawgeti(L, 1, i + 1);
if (ty != LUA_TTABLE) FAIL("program arglist must be table");
size_t argc = lua_rawlen(L, 2);
if (argc == 0) FAIL("need at least one argument to program");
argvs[i] = CKN(calloc(argc + 1, sizeof(char*)));
for (int j = 0; j < argc; j++) {
int ty = lua_rawgeti(L, 2, j + 1);
if (ty != LUA_TSTRING) FAIL("program argument must be string");
size_t slen = 0; char *str = lua_tolstring(L, 3, &slen);
argvs[i][j] = CKN(calloc(slen + 1, sizeof(char)));
memcpy(argvs[i][j], str, slen);
argvs[i][j][slen] = '\0'; // just to make sure
lua_pop(L, 1);
}
argvs[i][argc] = NULL; // just to make sure
lua_pop(L, 1);
}
char *inputstr = NULL; size_t inputlen = 0;
lua_pushliteral(L, "input");
int ty = lua_rawget(L, 1);
switch (ty) {
case LUA_TNIL: break;
case LUA_TSTRING:
inputstr = lua_tolstring(L, 2, &inputlen);
break;
default: FAIL("input field must be string if present");
}
size_t outlen;
outbuf = run(nprogs, argvs, inputlen, inputstr, &outlen);
lua_pushlstring(L, outbuf, outlen);
finish:
if (argvs != NULL) {
for (int i = 0; i < nprogs; i++) {
if (argvs[i] != NULL) {
for (int j = 0; argvs[i][j] != NULL; j++) {
free(argvs[i][j]);
}
free(argvs[i]);
}
}
free(argvs);
}
free(outbuf);
if (fail) return lua_error(L);
return 1;
}
int convienience_wrapper(lua_State *L) {
luaL_checktype(L, 1, LUA_TTABLE);
if (lua_gettop(L) != 1) return luaL_error(L, "run needs exactly 1 argument");
size_t tlen = lua_rawlen(L, 1);
if (tlen == 0) return luaL_error(L, "run's argument can't have 0 length");
int ty = lua_rawgeti(L, 1, 1);
lua_pop(L, 1);
if (ty == LUA_TSTRING) {
// x1 = {"a","b","c",input="ahaha"}
// x2 := {x1,input="ahaha"}
lua_newtable(L);
lua_pushvalue(L, 1);
lua_rawseti(L, 2, 1);
lua_pushliteral(L, "input");
lua_pushliteral(L, "input");
lua_rawget(L, 1);
lua_rawset(L, 2);
lua_replace(L, 1);
}
return do_the_thing(L);
}
int luaopen_run(lua_State *L) {
lua_pushcfunction(L, &convienience_wrapper);
return 1;
}
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