Add simple tokenizer

os.c

@@ -0,0 +1,59 @@
+
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <unistd.h>
+#include "s8slice.h"
+
+#include <stdio.h>
+
+enum {
+	OS_READ  = 1<<0,
+	OS_WRITE = 1<<1,
+	OS_ALLFLAGS = (1<<2)-1
+};
+typedef unsigned int os_open_flags;
+
+S8Slice os_open_file(S8Slice path, os_open_flags flags)
+{
+	int oflag = 0;
+	switch (flags & (OS_ALLFLAGS)) {
+		case OS_READ:
+			oflag = O_RDONLY;
+			break;
+		case OS_WRITE:
+			oflag = O_WRONLY;
+			break;
+		case OS_READ | OS_WRITE:
+			oflag = O_RDWR;
+	}
+	int fd = open((const char*)path.data, oflag);
+	if (fd == -1) {
+		goto open_fail;
+	}
+
+	struct stat st;
+	int ok = fstat(fd, &st);
+	if (ok == -1) {
+		goto fstat_fail;
+	}
+	
+	int prot = 0;
+	if (flags & OS_READ)  prot |= PROT_READ;
+	if (flags & OS_WRITE) prot |= PROT_WRITE;
+	void *x = mmap(NULL, st.st_size, prot, MAP_SHARED, fd, 0);
+	if (x == MAP_FAILED) {
+		goto mmap_fail;
+	}
+
+	close(fd);
+
+	return (S8Slice){.data = x, .len = (int64_t)st.st_size};
+
+mmap_fail:
+fstat_fail:
+	close(fd);
+open_fail:
+	return (S8Slice){.len = -1, .data = (uint8_t*)"<open_file error type>"};
+}