strans/ipc.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include "ipc.h"

#if !defined(MSG_NOSIGNAL) && !defined(SO_NOSIGPIPE)
#error "ipcsend requires MSG_NOSIGNAL or SO_NOSIGPIPE"
#endif

static void
putlen(unsigned char p[Ipclensz], size_t n)
{
	p[0] = n;
	p[1] = n >> 8;
}

static size_t
getlen(const unsigned char p[Ipclensz])
{
	return p[0] | (p[1] << 8);
}

int
ipcpath(char *dst, size_t cap)
{
	const char *dir, *sep;
	int n;

	if(dst == NULL || cap == 0)
		return -1;
	dir = getenv("XDG_RUNTIME_DIR");
	if(dir != NULL && dir[0] == '/'){
		sep = dir[strlen(dir)-1] == '/' ? "" : "/";
		n = snprintf(dst, cap, "%s%sstrans.sock", dir, sep);
	}else
		n = snprintf(dst, cap, "/tmp/strans.%lu",
			(unsigned long)getuid());
	if(n < 0 || (size_t)n >= cap)
		return -1;
	return 0;
}

int
ipcconnect(void)
{
	struct sockaddr_un addr;
	int e, fd;

	memset(&addr, 0, sizeof addr);
	addr.sun_family = AF_UNIX;
	if(ipcpath(addr.sun_path, sizeof addr.sun_path) < 0){
		errno = ENAMETOOLONG;
		return -1;
	}
	fd = socket(AF_UNIX, SOCK_STREAM, 0);
	if(fd < 0)
		return -1;
	if(connect(fd, (struct sockaddr*)&addr, sizeof addr) == 0)
		return fd;
	e = errno;
	close(fd);
	errno = e;
	return -1;
}

void
ipcpackreq(unsigned char req[Ipcreqsz], int want, unsigned int mod,
	unsigned int key)
{
	req[0] = want ? Ipcreqwant : 0;
	req[1] = mod;
	req[2] = key;
	req[3] = key >> 8;
	req[4] = key >> 16;
	req[5] = key >> 24;
}

void
ipcpackreset(unsigned char req[Ipcreqsz], int want)
{
	memset(req, 0, Ipcreqsz);
	req[0] = Ipcreqreset | (want ? Ipcreqwant : 0);
}

void
ipcunpackreq(const unsigned char req[Ipcreqsz], int *want, unsigned int *mod,
	unsigned int *key)
{
	*want = (req[0] & Ipcreqwant) != 0;
	*mod = req[1] & Mmask;
	*key = (unsigned int)req[2] |
		((unsigned int)req[3] << 8) |
		((unsigned int)req[4] << 16) |
		((unsigned int)req[5] << 24);
}

int
ipcreqreset(const unsigned char req[Ipcreqsz])
{
	return (req[0] & Ipcreqreset) != 0;
}

int
ipcpackresp(unsigned char *dst, size_t cap, int eaten,
	const char *commit, size_t ncommit, const char *preedit, size_t npreedit,
	int want)
{
	size_t n;

	if(ncommit > Ipcfieldmax || npreedit > Ipcfieldmax)
		return -1;
	if((ncommit > 0 && commit == NULL) ||
	   (want && npreedit > 0 && preedit == NULL))
		return -1;
	n = Ipcresphdrsz + ncommit + (want ? Ipclensz + npreedit : 0);
	if(dst == NULL || cap < n)
		return -1;
	dst[0] = eaten != 0;
	putlen(dst + 1, ncommit);
	if(ncommit > 0)
		memcpy(dst + Ipcresphdrsz, commit, ncommit);
	if(want){
		putlen(dst + Ipcresphdrsz + ncommit, npreedit);
		if(npreedit > 0)
			memcpy(dst + Ipcresphdrsz + ncommit + Ipclensz,
				preedit, npreedit);
	}
	return n;
}

int
ipcreadn(int fd, void *buf, size_t n)
{
	unsigned char *p;
	ssize_t r;

	p = buf;
	while(n > 0){
		r = read(fd, p, n);
		if(r < 0 && errno == EINTR)
			continue;
		if(r <= 0)
			return -1;
		p += r;
		n -= r;
	}
	return 0;
}

int
ipcsend(int fd, const void *buf, size_t n)
{
	const unsigned char *p;
	ssize_t r;
	int flags;
#if !defined(MSG_NOSIGNAL) && defined(SO_NOSIGPIPE)
	int one, sr;
#endif

	p = buf;
#ifdef MSG_NOSIGNAL
	flags = MSG_NOSIGNAL;
#else
	flags = 0;
#ifdef SO_NOSIGPIPE
	one = 1;
	do
		sr = setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof one);
	while(sr < 0 && errno == EINTR);
	if(sr < 0)
		return -1;
#endif
#endif
	while(n > 0){
		r = send(fd, p, n, flags);
		if(r < 0 && errno == EINTR)
			continue;
		if(r <= 0)
			return -1;
		p += r;
		n -= r;
	}
	return 0;
}

static int
readfield(int fd, size_t n, char *dst, size_t cap)
{
	unsigned char discard[128];
	size_t keep, part;

	if(cap > 0 && dst == NULL)
		return -1;
	keep = 0;
	if(cap > 0)
		keep = n >= cap ? cap - 1 : n;
	if(keep > 0 && ipcreadn(fd, dst, keep) < 0)
		return -1;
	if(cap > 0)
		dst[keep] = '\0';
	n -= keep;
	while(n > 0){
		part = n < sizeof discard ? n : sizeof discard;
		if(ipcreadn(fd, discard, part) < 0)
			return -1;
		n -= part;
	}
	return 0;
}

int
ipcreadresp(int fd, int want, char *commit, size_t ccap,
	char *preedit, size_t pcap, Ipcresp *resp)
{
	unsigned char hdr[Ipcresphdrsz], npreedit[Ipclensz];

	if(resp == NULL || (ccap > 0 && commit == NULL) ||
	   (pcap > 0 && preedit == NULL))
		return -1;
	if(ccap > 0)
		commit[0] = '\0';
	if(pcap > 0)
		preedit[0] = '\0';
	memset(resp, 0, sizeof *resp);
	if(ipcreadn(fd, hdr, sizeof hdr) < 0)
		return -1;
	resp->eaten = hdr[0] != 0;
	resp->ncommit = getlen(hdr + 1);
	if(resp->ncommit > Ipcfieldmax)
		return -1;
	if(readfield(fd, resp->ncommit, commit, ccap) < 0)
		return -1;
	if(!want)
		return 0;
	if(ipcreadn(fd, npreedit, sizeof npreedit) < 0)
		return -1;
	resp->npreedit = getlen(npreedit);
	if(resp->npreedit > Ipcfieldmax)
		return -1;
	return readfield(fd, resp->npreedit, preedit, pcap);
}