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	open.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	---
	open.c (1082B)
	---
	1 #define _GNU_SOURCE /* for Linux O_DIRECT */
	2 #include <u.h>
	3 #define NOPLAN9DEFINES
	4 #include <sys/file.h>
	5 #include <libc.h>
	6 #ifndef O_DIRECT
	7 #define O_DIRECT 0
	8 #endif
	9
	10 int
	11 p9open(char *name, int mode)
	12 {
	13 int cexec, rclose;
	14 int fd, umode, lock, rdwr;
	15 struct flock fl;
	16
	17 rdwr = mode&3;
	18 umode = rdwr;
	19 cexec = mode&OCEXEC;
	20 rclose = mode&ORCLOSE;
	21 lock = mode&OLOCK;
	22 mode &= ~(3\|OCEXEC\|ORCLOSE\|OLOCK);
	23 if(mode&OTRUNC){
	24 umode \|= O_TRUNC;
	25 mode ^= OTRUNC;
	26 }
	27 if(mode&ODIRECT){
	28 umode \|= O_DIRECT;
	29 mode ^= ODIRECT;
	30 }
	31 if(mode&ONONBLOCK){
	32 umode \|= O_NONBLOCK;
	33 mode ^= ONONBLOCK;
	34 }
	35 if(mode&OAPPEND){
	36 umode \|= O_APPEND;
	37 mode ^= OAPPEND;
	38 }
	39 if(mode){
	40 werrstr("mode 0x%x not supported", mode);
	41 return -1;
	42 }
	43 fd = open(name, umode);
	44 if(fd >= 0){
	45 if(lock){
	46 fl.l_type = (rdwr==OREAD) ? F_RDLCK : F_WRLCK;
	47 fl.l_whence = SEEK_SET;
	48 fl.l_start = 0;
	49 fl.l_len = 0;
	50 if(fcntl(fd, F_SETLK, &fl) < 0){
	51 close(fd);
	52 werrstr("lock: %r");
	53 return -1;
	54 }
	55 }
	56 if(cexec)
	57 fcntl(fd, F_SETFL, FD_CLOEXEC);
	58 if(rclose)
	59 remove(name);
	60 }
	61 return fd;
	62 }