add sys.writefile; support for darwin only in this CL

SVN=127153

src/cmd/gc/sys.go

@@ -53,6 +53,7 @@ func	gosched();
 func	goexit();
 
 func	readfile(string) (string, bool);	// read file into string; boolean status
+func	writefile(string, string) (bool);	// write string into file; boolean status
 func	bytestorune(*byte, int32, int32) (int32, int32);	// convert bytes to runes	
 func	stringtorune(string, int32, int32) (int32, int32);	// convert bytes to runes	
 
@@ -113,6 +114,7 @@ export
 
 	// files
 	readfile
+	writefile
 
 	// runes and utf-8
 	bytestorune

src/runtime/runtime.h

@@ -196,8 +196,9 @@ void*	mal(uint32);
 uint32	cmpstring(string, string);
 void	initsig(void);
 void	traceback(uint8 *pc, uint8 *sp, G* gp);
-int32	open(byte*, int32);
+int32	open(byte*, int32, ...);
 int32	read(int32, void*, int32);
+int32	write(int32, void*, int32);
 void	close(int32);
 int32	fstat(int32, void*);
 

src/runtime/sys_amd64_darwin.s

@@ -26,6 +26,7 @@ TEXT	sys·write(SB),1,$-8
 TEXT	open(SB),1,$-8
 	MOVQ	8(SP), DI
 	MOVL	16(SP), SI
+	MOVL	20(SP), DX
 	MOVQ	$0, R10
 	MOVL	$(0x2000000+5), AX	// syscall entry
 	SYSCALL
@@ -52,6 +53,14 @@ TEXT	read(SB),1,$-8
 	SYSCALL
 	RET
 
+TEXT	write(SB),1,$-8
+	MOVL	8(SP), DI
+	MOVQ	16(SP), SI
+	MOVL	24(SP), DX
+	MOVL	$(0x2000000+4), AX	// syscall entry
+	SYSCALL
+	RET
+
 TEXT	sys·sigaction(SB),1,$-8
 	MOVL	8(SP), DI		// arg 1 sig
 	MOVQ	16(SP), SI		// arg 2 act

src/runtime/sys_file.c

@@ -37,12 +37,39 @@ sys·readfile(string filein, string fileout, bool okout)
 		fileout = nil;
 		goto close_out;
 	}
-	okout = 1;
+	okout = true;
 
 close_out:
 	close(fd);
 out:
 	FLUSH(&fileout);
 	FLUSH(&okout);
-	return;
+}
+
+void
+sys·writefile(string filein, string textin, bool okout)
+{
+	int32 fd;
+	byte namebuf[256];
+
+	okout = false;
+
+	if(filein == nil || filein->len >= sizeof(namebuf))
+		goto out;
+
+	mcpy(namebuf, filein->str, filein->len);
+	namebuf[filein->len] = '\0';
+	fd = open(namebuf, 1|0x0200, 0644);  // open for write, create if non-existant (sic)
+	if(fd < 0)
+		goto out;
+
+	if (write(fd, textin->str, textin->len) != textin->len) {
+		goto close_out;
+	}
+	okout = true;
+
+close_out:
+	close(fd);
+out:
+	FLUSH(&okout);
 }