1 files changed, 102 insertions, 0 deletions
diff --git a/c/cat/cat.c b/c/cat/cat.c
new file mode 100644
index 0000000..7aaaa6b
--- /dev/null
+++ b/c/cat/cat.c
@@ -0,0 +1,102 @@
+#include <sys/sendfile.h>
+#include <sys/stat.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define warn(...) \
+	do { \
+		warn(__VA_ARGS__); \
+		rv = EXIT_FAILURE; \
+	} while (0)
+
+static int rv = EXIT_SUCCESS;
+static bool out_is_reg;
+static char buf[BUFSIZ];
+
+static void cat(const char *);
+static void cat_sendfile(const char *, int, size_t);
+static void cat_readwrite(const char *, int);
+
+int
+main(int argc, char **argv)
+{
+	struct stat sb;
+
+	if (fstat(STDOUT_FILENO, &sb) == -1)
+		warn("fstat: /dev/stdout");
+	else
+		out_is_reg = S_ISREG(sb.st_mode);
+
+	if (argc == 1)
+		cat("-");
+	for (int i = 1; i < argc; i++)
+		cat(argv[i]);
+	return rv;
+}
+
+void
+cat(const char *file)
+{
+	int fd;
+	struct stat sb;
+
+	if (strcmp(file, "-") == 0)
+		fd = STDIN_FILENO;
+	else if ((fd = open(file, O_RDONLY)) == -1) {
+		warn("open: %s", file);
+		return;
+	}
+
+	if (fstat(fd, &sb) == -1) {
+		warn("fstat: %s", file);
+		goto out;
+	}
+
+	if (S_ISREG(sb.st_mode) && out_is_reg)
+		cat_sendfile(file, fd, sb.st_size);
+	else
+		cat_readwrite(file, fd);
+
+out:
+	close(fd);
+}
+
+void
+cat_sendfile(const char *file, int fd, size_t n)
+{
+	off_t off = 0;
+	ssize_t nw;
+
+	do {
+		nw = sendfile(STDOUT_FILENO, fd, &off, n);
+		off += nw;
+	} while (nw != -1 && (size_t)off < n);
+
+	if (nw == -1)
+		warn("sendfile: %s", file);
+}
+
+void
+cat_readwrite(const char *file, int fd)
+{
+	ssize_t nr, nw;
+
+	while ((nr = read(fd, buf, BUFSIZ)) > 0) {
+		for (ssize_t off = 0; nr > 0; nr -= nw, off += nw) {
+			if ((nw = write(STDOUT_FILENO, buf + off, nr)) == -1) {
+				warn("write: %s", file);
+				return;
+			}
+		}
+	}
+	if (nr == -1)
+		warn("read: %s", file);
+}