add simple piping program for host

2 files changed, 59 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index da43892..6ced357 100644
--- a/Makefile
+++ b/Makefile
@@ -47,7 +47,10 @@ qemu-bin : kernel7.img
 qemu-loader : loader.img
 	qemu-system-arm -m 256 -M raspi2 -serial stdio -kernel $^
 
+pipe_image : pipe_image.c
+	gcc -Wall -std=gnu99 -O3 $^ -o $@
+
 clean :
-	-rm *.img *.elf *.o
+	-rm *.img *.elf *.o pipe_image
 
 .PHONY: all qemu-elf qemu-bin clean
diff --git a/pipe_image.c b/pipe_image.c
new file mode 100644
index 0000000..7e24ea7
--- /dev/null
+++ b/pipe_image.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <err.h>
+#include <endian.h>
+#include <stdint.h>
+#include <sys/types.h>
+
+#define ANSI_FG_RED "\033[0;31m"
+
+/* This program pipes it's argument file to stdout prepending it */
+/* with it's size (4 bytes, little endian). It is intended to be used */
+/* with our bootloader (i.e. by piping kernel image to UART). */
+
+int main(int argc, char **argv) {
+  char *image_file_name = argc > 1 ? argv[1] : "kernel7.img";
+  
+  FILE *image_file_handle = fopen(image_file_name, "r");
+
+  if (!image_file_handle)
+    err(-1, "couldn't open" ANSI_FG_RED "%s", image_file_name);
+
+  if (fseek(image_file_handle, 0, SEEK_END))
+    err(-1, "error navigating through file");
+
+  ssize_t image_size = ftell(image_file_handle);
+  if (image_size < 0)
+    err(-1, "couldn't get image file size");
+
+  if (image_size >> 32)
+    err(-1, "file to big (should be smaller than 4G)");
+
+  if (fseek(image_file_handle, 0, SEEK_SET))
+    err(-1, "error navigating through file");
+
+  uint32_t image_size_le = htole32(image_size);
+
+  if (fwrite(&image_size_le, 4, 1, stdout) != 1)
+    err(-1, "couldn't write to stdout");
+
+  ssize_t bytes_left = image_size;
+  
+  char buf[1024];
+
+  while (bytes_left)
+    {
+      size_t bytes_read;
+      if ((bytes_read = fread(buf, 1, sizeof(buf), image_file_handle))
+	  < 1)
+	err(-1, "error reading the file");
+
+      if (fwrite(buf, bytes_read, 1, stdout) != 1)
+	err(-1, "error writing to stdout");
+
+      bytes_left -= bytes_read;
+    }
+}