From: Scott Worley <scottworley@scottworley.com>
Date: Sat, 6 May 2017 18:42:47 +0000 (-0700)
Subject: Make a function call interface
X-Git-Url: http://git.scottworley.com/overonion/commitdiff_plain/b398ee5ae7abfa019f84628204f3c1cd146ed39e?ds=inline

Make a function call interface
---

diff --git a/Makefile b/Makefile
index fee4ea9..71a482e 100644
--- a/Makefile
+++ b/Makefile
@@ -14,7 +14,7 @@ depend: *.c
 
 .PHONY: clean distclean depend
 
-reverse: reverse.o
+reverse: reverse.o reverse_lib.o
 	$(CC) -o $@ $^ $(CFLAGS)
 
 %.o: %.c
diff --git a/reverse.c b/reverse.c
index ac55a10..2d83751 100644
--- a/reverse.c
+++ b/reverse.c
@@ -1,70 +1,14 @@
-#define _FILE_OFFSET_BITS 64
+#include "reverse_lib.h"
 
-#define BUFFER_SIZE 4096
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/mman.h>
-#include <fcntl.h>
-#include <unistd.h>
 #include <err.h>
 #include <sysexits.h>
 
-void write_all(int fd, const void *buf, size_t count) {
-  const char* cbuf = buf;
-  size_t written = 0;
-  while (written < count) {
-    int ret = write(fd, &cbuf[written], count - written);
-    if (ret == -1) {
-      err(EX_IOERR, "Could not write");
-    }
-    written += ret;
-  }
-}
-
-
 int main(int argc, char** argv) {
   if (argc != 2) {
     errx(EX_USAGE, "Usage: reverse filename");
   }
 
-  int fd = open(argv[1], O_RDONLY);
-  if (fd == -1) {
-    err(EX_NOINPUT, "Could not open specified file");
-  }
-
-  struct stat stats;
-  if (fstat(fd, &stats) == -1) {
-    err(EX_NOINPUT, "Could not stat input");
-  }
-
-  long page_size = sysconf(_SC_PAGE_SIZE);
-  off_t pages = (stats.st_size - 1) / page_size + 1;
-  long map_size = pages * page_size;
-  char *m = mmap(NULL, map_size, PROT_READ, MAP_SHARED, fd, 0);
-  if (m == MAP_FAILED) {
-    err(EX_NOINPUT, "Could not mmap input");
-  }
-
-  char buf[BUFFER_SIZE];
-  off_t buf_offset = 0;
-  for (off_t p = stats.st_size - 1; p >= 0; p--) {
-    buf[buf_offset++] = m[p];
-    if (buf_offset >= BUFFER_SIZE) {
-      write_all(1, buf, buf_offset);
-      buf_offset = 0;
-    }
-  }
-  if (buf_offset) {
-    write_all(1, buf, buf_offset);
-  }
-
-  if (munmap(m, map_size) == -1) {
-    err(EX_IOERR, "Could not unmap input");
-  }
-  if (close(fd) == -1) {
-    err(EX_IOERR, "Could not close input");
-  }
+  reverse_file(argv[1]);
 
   return 0;
 }
diff --git a/reverse_lib.c b/reverse_lib.c
new file mode 100644
index 0000000..a800db8
--- /dev/null
+++ b/reverse_lib.c
@@ -0,0 +1,63 @@
+#define _FILE_OFFSET_BITS 64
+
+#define BUFFER_SIZE 4096
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <err.h>
+#include <sysexits.h>
+
+static void write_all(int fd, const void *buf, size_t count) {
+  const char* cbuf = buf;
+  size_t written = 0;
+  while (written < count) {
+    int ret = write(fd, &cbuf[written], count - written);
+    if (ret == -1) {
+      err(EX_IOERR, "Could not write");
+    }
+    written += ret;
+  }
+}
+
+void reverse_file(const char* input_filename) {
+  int fd = open(input_filename, O_RDONLY);
+  if (fd == -1) {
+    err(EX_NOINPUT, "Could not open specified file");
+  }
+
+  struct stat stats;
+  if (fstat(fd, &stats) == -1) {
+    err(EX_NOINPUT, "Could not stat input");
+  }
+
+  long page_size = sysconf(_SC_PAGE_SIZE);
+  off_t pages = (stats.st_size - 1) / page_size + 1;
+  long map_size = pages * page_size;
+  char *m = mmap(NULL, map_size, PROT_READ, MAP_SHARED, fd, 0);
+  if (m == MAP_FAILED) {
+    err(EX_NOINPUT, "Could not mmap input");
+  }
+
+  char buf[BUFFER_SIZE];
+  off_t buf_offset = 0;
+  for (off_t p = stats.st_size - 1; p >= 0; p--) {
+    buf[buf_offset++] = m[p];
+    if (buf_offset >= BUFFER_SIZE) {
+      write_all(1, buf, buf_offset);
+      buf_offset = 0;
+    }
+  }
+  if (buf_offset) {
+    write_all(1, buf, buf_offset);
+  }
+
+  if (munmap(m, map_size) == -1) {
+    err(EX_IOERR, "Could not unmap input");
+  }
+  if (close(fd) == -1) {
+    err(EX_IOERR, "Could not close input");
+  }
+}
diff --git a/reverse_lib.h b/reverse_lib.h
new file mode 100644
index 0000000..58345fa
--- /dev/null
+++ b/reverse_lib.h
@@ -0,0 +1,8 @@
+#ifndef _OVERONION_REVERSE_LIB_H
+#define _OVERONION_REVERSE_LIB_H
+
+/* Copy the contents of input_filename to stdout backwards.
+ * input_filename must be a real file, not a pipe. */
+void reverse_file(const char* input_filename);
+
+#endif /* _OVERONION_REVERSE_LIB_H */