1 files changed, 127 insertions, 0 deletions
diff --git a/idkey/main.c b/idkey/main.c
new file mode 100644
index 0000000..16b2232
--- /dev/null
+++ b/idkey/main.c
@@ -0,0 +1,127 @@
+#include <fcntl.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define EXIT_SUCCESS		0
+#define EXIT_CMDLINE		1
+#define EXIT_FILEOPEN		2
+#define EXIT_FILEREAD		3
+#define EXIT_FILEWRITE		4
+#define EXIT_INVALID		5
+#define EXIT_ALLOC			6
+
+#define BLOCK_SIZE			4096
+
+/// @brief Header of the datas.
+typedef struct header_
+{
+	char mn[4];
+	size_t size;
+} header;
+
+/// @brief Check if the @c v is a valid magick number.
+/// @param[in] v magick number.
+/// @return 1 if valid, zero otherwise.
+int is_valid_nm(const char* v)
+{
+	return v && v[0] == 'I' && v[1] == 'D' && v[2] == 'K' && v[3] == 'Y';
+}
+
+/// @brief Close the file descriptor if valid then print a formatted error message then return the specified code.
+/// @param[in] fd File descriptor to close.
+/// @param[in] code The exit code to return.
+/// @param[in] format The message to print.
+/// @param[in] ... Values for formatting.
+/// @return The exit code provided by @c code.
+int close_and_fail(int fd, int code, const char* format, ...)
+{
+	va_list arglist;
+	fprintf(stderr, "Error: ");
+	va_start(arglist, format);
+	vfprintf(stderr, format, arglist);
+	va_end(arglist);
+	fprintf(stderr, "\n");
+	return code;
+}
+
+/// @brief Read the device @c devname and print it's data to stdout.
+/// @param[in] devname Device's name.
+/// @return Exit code, zero if success.
+int read_device(const char* devname)
+{
+	int fd = open(devname, O_RDONLY);
+	if (fd == -1) return close_and_fail(fd, EXIT_FILEOPEN, "Failed to open '%s'!", devname);
+
+	header h;
+	ssize_t sz = read(fd, &h, sizeof(header));
+	if (sz != sizeof(header)) return close_and_fail(fd, EXIT_FILEREAD, "Failed to read the header!");
+	if (!is_valid_nm(h.mn)) return close_and_fail(fd, EXIT_INVALID, "Not a valid identity key!");
+
+	while(h.size)
+	{
+		char datas[BLOCK_SIZE + 1];
+		memset(datas, BLOCK_SIZE +1, 0);
+		size_t count = BLOCK_SIZE > h.size ? h.size : BLOCK_SIZE;
+
+		sz = read(fd, datas, count);
+
+		if (sz != count) close_and_fail(fd, EXIT_FILEREAD, "Failed to read a data block!");
+		h.size = (h.size - count);
+
+		printf(datas);
+	}
+	printf("\n");
+	close(fd);
+	return EXIT_SUCCESS;
+}
+
+/// @brief Write the specified data to the specified device.
+/// @param[in] devname Name of the device.
+/// @param[in] datas Datas to write.
+/// @return Exit code, zero if success, non-zero otherwise.
+int write_device(const char* devname, const char* datas)
+{
+	header h = {
+		.mn = {'I', 'D', 'K', 'Y'},
+		.size = strlen(datas)
+	};
+	if (h.size < 1) return close_and_fail(-1, EXIT_CMDLINE, "No data to write!");
+
+	int fd = open(devname, O_WRONLY);
+	if (fd == -1) return close_and_fail(fd, EXIT_FILEOPEN, "Failed to open device '%s'!", devname);
+	if (write(fd, &h, sizeof(header)) != sizeof(header)) return close_and_fail(fd, EXIT_FILEWRITE, "Failed to write the header!");
+	if (write(fd, datas, h.size) != h.size) return close_and_fail(fd, EXIT_FILEWRITE, "Failed to write datas!");
+	
+	close(fd);
+	return EXIT_SUCCESS;
+}
+
+/// @brief Entry point.
+/// @param[in] argc Number of arguments in @c argv.
+/// @param[in] argv Arguments array.
+/// @return Exit code, zero if success, non-zero otherwise.
+int main(int argc, char** argv)
+{
+	switch(argc)
+	{
+	case 0:
+	case 1:
+		fprintf(stderr, "ERROR: too few arguments!\n");
+		return EXIT_CMDLINE;
+
+	case 2: // Read the device
+		return read_device(argv[1]);
+
+	case 3: // Write the device
+		return write_device(argv[1], argv[2]);
+
+	default:
+		fprintf(stderr, "ERROR: too many arguments!\n");
+		return EXIT_CMDLINE;
+	}
+}
+