splice

commit 6da6771b247ef295105099dd62297bad82bfd502
parent 03ba9c7da68c3fadb64ca32dbc9258919b7ac19a
Author: Louis Burda <quent.burda@gmail.com>
Date:   Mon, 13 Mar 2023 14:46:01 +0100

Rename to splice

Diffstat:
M
.gitignore
 | 
2
+-
M
Makefile
 | 
17
+++++++++++++----
D
binpatch.c
 | 
54
------------------------------------------------------
A
splice.c
 | 
60
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

4 files changed, 74 insertions(+), 59 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -1 +1 @@
-binpatch
+splice
diff --git a/Makefile b/Makefile
@@ -1,10 +1,19 @@
+PREFIX ?= /usr/local
+BINDIR ?= /bin
+
 CFLAGS = -g
 
-all: binpatch
+all: splice
 
 clean:
-	rm -f binpatch
+	rm -f splice
+
+splice: splice.c
+
+install:
+	install -m 755 splice -t "$(DESTDIR)$(PREFIX)$(BINDIR)"
 
-binpatch: binpatch.c
+uninstall:
+	rm -f "$(DESTDIR)$(PREFIX)$(BINDIR)/splice"
 
-.PHONY: all clean
+.PHONY: all clean install uninstall
diff --git a/binpatch.c b/binpatch.c
@@ -1,54 +0,0 @@
-#include <err.h>
-#include <stdio.h>
-#include <stdint.h>
-#include <stdlib.h>
-
-int
-main(int argc, const char **argv)
-{
-	ssize_t addr, size;
-	char *end, *data;
-	FILE *file;
-	int ret;
-
-	if (argc != 4) {
-		printf("USAGE: fwpatch TARGET OFFSET FILE\n");
-		return 0;
-	}
-
-	addr = strtoull(argv[2], &end, 0);
-	if (*end) err(1, "strtoull %s", argv[2]);
-
-	file = fopen(argv[3], "rb");
-	if (!file) err(1, "fopen %s", argv[3]);
-
-	ret = fseek(file, 0, SEEK_END);
-	if (ret < 0) err(1, "fseek %s", argv[3]);
-
-	size = ftell(file);
-	if (size < 0) err(1, "ftell %s", argv[3]);
-
-	data = malloc(size);
-	if (!data) err(1, "malloc %lu", size);
-
-	ret = fseek(file, 0, SEEK_SET);
-	if (ret < 0) err(1, "freek %s", argv[3]);
-
-	if (fread(data, 1, size, file) != size)
-		errx(1, "fread %lu", size);
-
-	fclose(file);
-
-	file = fopen(argv[1], "r+b");
-	if (!file) err(1, "fopen %s", argv[1]);
-
-	ret = fseek(file, addr, SEEK_SET);
-	if (ret < 0) err(1, "fseek %s", argv[1]);
-
-	if (fwrite(data, 1, size, file) != size)
-		errx(1, "fwrite %lu", size);
-
-	fclose(file);
-
-	free(data);
-}
diff --git a/splice.c b/splice.c
@@ -0,0 +1,60 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+int
+main(int argc, const char **argv)
+{
+	char buf[BUFSIZ];
+	ssize_t start, end;
+	ssize_t pos, nread, nreq;
+	FILE *main_file;
+	char *endc;
+	int ret;
+
+	if (argc < 3 || argc > 4) {
+		printf("USAGE: fwpatch MAIN START [END]\n");
+		return 0;
+	}
+
+	main_file = fopen(argv[1], "rb");
+	if (!main_file) err(1, "fopen %s", argv[1]);
+
+	start = strtoll(argv[2], &endc, 0);
+	if (endc && *endc) err(1, "strtoll %s", argv[2]);
+	if (start < 0) errx(1, "negative start");
+
+	if (argc == 4) {
+		end = strtoll(argv[3], &endc, 0);
+		if (endc && *endc) err(1, "strtoll %s", argv[3]);
+		if (start >= end) errx(1, "invalid length");
+	} else {
+		end = -1;
+	}
+
+	pos = 0;
+	while (!feof(main_file) || !feof(stdin)) {
+		if (pos >= start && !feof(stdin)) {
+			nread = fread(buf, 1, BUFSIZ, stdin);
+			if (pos == start && end >= 0)
+				fseek(main_file, end, SEEK_CUR);
+			else if (end < 0)
+				fseek(main_file, nread, SEEK_CUR);
+		} else {
+			if (start > pos) {
+				nreq = start - pos;
+				if (nreq > BUFSIZ)
+					nreq = BUFSIZ;
+			} else {
+				nreq = BUFSIZ;
+			}
+			nread = fread(buf, 1, nreq, main_file);
+		}
+		if (fwrite(buf, 1, nread, stdout) != nread)
+			errx(1, "output truncated");
+		pos += nread;
+	}
+
+	fclose(main_file);
+}