base58check.c: implement hex data input/output + other enhancements

base58check.c

@@ -7,26 +7,58 @@
 #include <getopt.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <sysexits.h>
-#include <unistd.h>
 
 
 static void print_usage() {
-	fprintf(stderr, "usage: %s [-d]\n\n"
+	fprintf(stderr, "usage: %s [-d] [-h]\n\n"
 		"Reads data from stdin, encodes it in Base58Check, and writes the encoding to\n"
-		"stdout. Specify -d to decode instead.\n",
+		"stdout. Specify -d to decode instead. Specify -h to use hex data input/output.\n",
 		program_invocation_short_name);
 }
 
+static int gethex() {
+	static const int8_t DECODE['f' + 1 - '0'] = {
+		 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
+		-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+		-1, 10, 11, 12, 13, 14, 15
+	};
+	int hi, lo;
+	if ((hi = getchar()) < 0)
+		return hi;
+	if ((hi -= '0') >= 0 && hi <= 'f' - '0' && (hi = DECODE[hi]) >= 0) {
+		if ((lo = getchar()) >= 0 && (lo -= '0') >= 0 && lo <= 'f' - '0' && (lo = DECODE[lo]) >= 0)
+			return hi << 4 | lo;
+	}
+	else if (hi == '\n' - '0')
+		return EOF;
+	errx(EX_DATAERR, "invalid hex on stdin");
+}
+
+static ssize_t fwrite_hex(const unsigned char in[], size_t n_in, FILE *out) {
+	static const char ENCODE[16] = {
+		'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+	};
+	for (size_t i = 0; i < n_in; ++i) {
+		char x[2] = { ENCODE[in[i] >> 4], ENCODE[in[i] & 0xF] };
+		if (fwrite(x, 1, 2, out) < 2)
+			return -1;
+	}
+	return putc('\n', out) < 0 ? -1 : (ssize_t) n_in;
+}
+
 int main(int argc, char *argv[]) {
 	static const struct option longopts[] = {
 		{ .name = "decode", .has_arg = no_argument, .val = 'd' },
+		{ .name = "hex", .has_arg = no_argument, .val = 'h' },
 		{ .name = "help", .has_arg = no_argument, .val = 1 },
 		{ .name = "version", .has_arg = no_argument, .val = 2 },
 		{ }
 	};
-	bool decode = false;
-	for (int opt; (opt = getopt_long(argc, argv, "d", longopts, NULL)) >= 0;) {
+	bool decode = false, hex = false;
+	for (int opt; (opt = getopt_long(argc, argv, "dh", longopts, NULL)) >= 0;) {
 		switch (opt) {
 			case 1:
 				print_usage();
@@ -37,36 +69,56 @@ int main(int argc, char *argv[]) {
 			case 'd':
 				decode = true;
 				break;
+			case 'h':
+				hex = true;
+				break;
 			default:
 				print_usage();
 				return EX_USAGE;
 		}
 	}
+	if (optind != argc)
+		return print_usage(), EX_USAGE;
 
 	unsigned char in[4096];
 	size_t n_in = 0;
-
-	for (size_t r; n_in < sizeof in && (r = fread(in + n_in, 1, sizeof in - n_in, stdin)) > 0; n_in += r);
-	if (ferror(stdin) || n_in == sizeof in)
-		return EX_IOERR;
+	if (decode || hex) {
+		for (int c;;) {
+			if (decode ? (c = getchar()) < 0 || c == '\n' : (c = gethex()) < 0) {
+				if (ferror(stdin))
+					err(EX_IOERR, "error reading from stdin");
+				break;
+			}
+			if (n_in == sizeof in)
+				errx(EX_DATAERR, "input is too long");
+			in[n_in++] = (unsigned char) c;
+		}
+	}
+	else {
+		n_in = fread(in, 1, sizeof in, stdin);
+		if (ferror(stdin))
+			err(EX_IOERR, "error reading from stdin");
+		if (!feof(stdin) && getchar() >= 0)
+			errx(EX_DATAERR, "input is too long");
+	}
 
 	unsigned char *out = NULL;
 	size_t n_out = 0;
 	if (decode) {
-		if (n_in && in[n_in - 1] == '\n')
-			in[--n_in] = '\0';
 		if (base58check_decode(&out, &n_out, (char *) in, n_in, 0))
 			errx(EX_DATAERR, "input was not a valid Base58Check encoding");
 	}
 	else {
 		n_out = 1;
 		if (base58check_encode((char **) &out, &n_out, in, n_in, 0))
-			return EX_UNAVAILABLE;
+			errx(EX_SOFTWARE, "internal error");
 		out[n_out++] = '\n';
 	}
 
-	if (fwrite(out, 1, n_out, stdout) < n_out)
-		return EX_IOERR;
+	if (hex && decode ?
+			fwrite_hex((const unsigned char *) out, n_out, stdout) < (ssize_t) n_out :
+			fwrite(out, 1, n_out, stdout) < n_out)
+		err(EX_IOERR, "error writing to stdout");
 
 	return EX_OK;
 }