luad

commit 7fdcc89ec178dd27d33629e301189d5d2d353e6f
parent e3bf89dcdf6588076e04a66bbb150671c84b0854
Author: Daniel Barlow <dan@telent.net>
Date:   Sun, 17 May 2026 23:57:42 +0100

WIP luac C translation

TODO wait for server to send script exit value

Diffstat:
A
luac.c
 | 
144
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 144 insertions(+), 0 deletions(-)
diff --git a/luac.c b/luac.c
@@ -0,0 +1,144 @@
+#include <unistd.h>
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <lualib.h>
+
+#include <sys/socket.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <sys/un.h>
+
+#include <arpa/inet.h>
+
+// copied from OpenBSD
+// https://github.com/openbsd/src/blob/master/lib/libc/string/strlcpy.c
+
+/*
+ * Copy string src to buffer dst of size dsize.  At most dsize-1
+ * chars will be copied.  Always NUL terminates (unless dsize == 0).
+ * Returns strlen(src); if retval >= dsize, truncation occurred.
+ */
+size_t strlcpy(char *dst, const char *src, size_t dsize)
+{
+    const char *osrc = src;
+    size_t nleft = dsize;
+
+    /* Copy as many bytes as will fit. */
+    if (nleft != 0) {
+        while (--nleft != 0) {
+            if ((*dst++ = *src++) == '\0')
+                break;
+        }
+    }
+
+    /* Not enough room in dst, add NUL and traverse rest of src. */
+    if (nleft == 0) {
+        if (dsize != 0)
+            *dst = '\0';		/* NUL-terminate dst */
+        while (*src++)
+            ;
+    }
+
+    return(src - osrc - 1);	/* count does not include NUL */
+}
+
+int open_socket(char * pathname){
+
+    struct sockaddr_un addr;
+    addr.sun_family = AF_UNIX;
+    addr.sun_path[0] = '\0';    /* abstract path */
+    strncpy(&addr.sun_path[1], pathname, sizeof(addr.sun_path) - 2);
+
+    int fd = socket(AF_LOCAL, SOCK_DGRAM, PF_LOCAL);
+    if(fd < 0) {
+        perror("socket");
+        exit(EXIT_FAILURE);
+    }
+
+    if((bind(fd, (struct sockaddr *) &addr, sizeof addr)) < 0) {
+        perror("bind");
+        exit(EXIT_FAILURE);
+    }
+    return fd;
+}
+
+int encode_args(char * buf, int len, int argc, char ** argv) {
+
+    char * buf_end = buf + len;
+    char * p = buf;
+    for (int i = 1; i < argc; i++) {
+        p += strlcpy(p, argv[i], buf_end - p);
+        if(p >= buf_end) {
+            fprintf(stderr, "comand line too long\n");
+            exit(1);
+        }
+        p++;
+    }
+    return p - buf;
+}
+
+int main(int argc, char **argv)
+{
+#ifdef TEST
+    char *test_args[] = //        { "luac", "john", "paul is dead", "ringo" };
+        { "luac", "hello.lua" };
+    write(1, encode_args(25, 2, test_args), 25);
+    char *test2_args[] = { // this is too long
+        "luac", "0123456789",  "0123456789", "012"
+    };
+    write(1, encode_args(25, 4, test2_args), 25);
+    exit(0);
+#endif
+
+    if (argc < 2) {
+        fprintf(stderr, "Usage: %s pathname.lua\n", argv[0]);
+        exit(1);
+    }
+
+    char * iobuf = (char *) calloc(1024, sizeof(char));
+    if(!iobuf) return 1;
+    int iobuf_len = encode_args(iobuf, 1024, argc, argv);
+
+    int maxnamelen=sizeof (((struct sockaddr_un *) 0)->sun_path);
+    char *sockname = calloc(maxnamelen, 1);
+    pid_t mypid = getpid();
+    memcpy(sockname, (void *) &mypid, sizeof mypid);
+    memcpy(sockname + sizeof mypid, iobuf, maxnamelen - sizeof mypid);
+
+    struct sockaddr_un peer_addr = { AF_UNIX, "/tmp/mysock" };
+    int socket = open_socket(sockname);
+    connect(socket, (struct sockaddr *) &peer_addr, sizeof peer_addr);
+
+    struct msghdr msg = { 0 };
+    struct cmsghdr *cmsg;
+    int myfds[] = {0,1,2};
+    struct iovec iov = {
+        .iov_base = iobuf,
+        .iov_len = iobuf_len
+    };
+    union {         /* Ancillary data buffer, wrapped in a union
+                       in order to ensure it is suitably aligned */
+        char buf[CMSG_SPACE(sizeof(myfds))];
+        struct cmsghdr align;
+    } u;
+
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = u.buf;
+    msg.msg_controllen = sizeof(u.buf);
+    cmsg = CMSG_FIRSTHDR(&msg);
+    cmsg->cmsg_level = SOL_SOCKET;
+    cmsg->cmsg_type = SCM_RIGHTS;
+    cmsg->cmsg_len = CMSG_LEN(sizeof(myfds));
+    memcpy(CMSG_DATA(cmsg), myfds, sizeof(myfds));
+
+    int bytes = sendmsg(socket, &msg, 0);
+    if(bytes <= 0) {
+        perror("sendmsg");
+        exit(1);
+    }
+
+    /* FIXME: wait for bytes on socket signifying return value */
+}