carmel: init a basic software package builder

programs/carmel/util.c

@@ -0,0 +1,76 @@
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "util.h"
+
+void
+copyFile(const char *source, const char *dest)
+{
+	char buffer[1024];
+	ssize_t ret;
+	int s, d;
+
+	if ((s = open(source, O_RDONLY)) == -1)
+		err(1, "cannot open %s", source);
+	if ((d = open(dest, O_WRONLY | O_CREAT, 0644)) == -1)
+		err(1, "cannot open %s", dest);
+
+	while ((ret = read(s, &buffer, 1024)) > 0) {
+		write(d, buffer, ret);
+	}
+
+	if (ret == -1)
+		err(1, "cannot read from %s", source);
+
+	close(s);
+	close(d);
+}
+
+void
+changeDirectory(const char *path)
+{
+	if (chdir(path) == -1)
+		err(1, "cd '%s'", path);
+}
+
+bool
+exists(const char *path)
+{
+	if (open(path, O_RDONLY) == -1) {
+		if (errno == ENOENT)
+			return 0;
+	}
+	return 1;
+}
+
+/*
+ * 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
+strbcpy(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 */
+}