New applet cksum, from Rob Sullivan.

coreutils/Config.in

@@ -52,6 +52,12 @@ config CONFIG_CHROOT
 	  chroot is used to change the root directory and run a command.
 	  The default command is `/bin/sh'.
 
+config CONFIG_CKSUM
+	bool "cksum"
+	default n
+	help
+	  cksum is used to calculate the CRC32 checksum of a file.
+
 config CONFIG_CMP
 	bool "cmp"
 	default n

coreutils/Makefile.in

@@ -18,6 +18,7 @@ COREUTILS-$(CONFIG_CHGRP)     += chgrp.o
 COREUTILS-$(CONFIG_CHMOD)     += chmod.o
 COREUTILS-$(CONFIG_CHOWN)     += chown.o
 COREUTILS-$(CONFIG_CHROOT)    += chroot.o
+COREUTILS-$(CONFIG_CKSUM)     += cksum.o
 COREUTILS-$(CONFIG_CMP)       += cmp.o
 COREUTILS-$(CONFIG_COMM)      += comm.o
 COREUTILS-$(CONFIG_CP)        += cp.o

coreutils/cksum.c

@@ -0,0 +1,56 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * cksum - calculate the CRC32 checksum of a file
+ *
+ * Copyright (C) 2006 by Rob Sullivan, with ideas from code by Walter Harms
+ * 
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include "busybox.h"
+
+int cksum_main(int argc, char **argv) {
+	
+	uint32_t *crc32_table = bb_crc32_filltable(1);
+
+	FILE *fp;
+	uint32_t crc;
+	long length, filesize;
+	int bytes_read;
+	char *cp;
+	RESERVE_CONFIG_BUFFER(buf, BUFSIZ);
+	int inp_stdin = (argc == optind) ? 1 : 0;
+	
+	do {
+		fp = bb_wfopen_input((inp_stdin) ? bb_msg_standard_input : *++argv);
+			
+		crc = 0;
+		length = 0;
+		
+		while ((bytes_read = fread(buf, 1, BUFSIZ, fp)) > 0) {
+			cp = buf;
+			length += bytes_read;
+			while (bytes_read--)
+				crc = (crc << 8) ^ crc32_table[((crc >> 24) ^ (*cp++)) & 0xffL];
+		}
+		
+		filesize = length;
+		
+		for (; length; length >>= 8)
+			crc = (crc << 8) ^ crc32_table[((crc >> 24) ^ length) & 0xffL];
+		crc ^= 0xffffffffL;
+
+		if (inp_stdin) {
+			printf("%"PRIu32" %li\n", crc, filesize);
+			break;
+		}
+		
+		printf("%"PRIu32" %li %s\n", crc, filesize, *argv);	
+		fclose(fp);
+	} while (*(argv+1));
+	
+	return EXIT_SUCCESS;
+}

include/applets.h

@@ -70,6 +70,7 @@ USE_CHMOD(APPLET(chmod, chmod_main, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_CHOWN(APPLET(chown, chown_main, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_CHROOT(APPLET(chroot, chroot_main, _BB_DIR_USR_SBIN, _BB_SUID_NEVER))
 USE_CHVT(APPLET(chvt, chvt_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
+USE_CKSUM(APPLET(cksum, cksum_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_CLEAR(APPLET(clear, clear_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_CMP(APPLET(cmp, cmp_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_COMM(APPLET(comm, comm_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))

include/usage.h

@@ -224,6 +224,11 @@
 #define chvt_full_usage \
 	"Changes the foreground virtual terminal to /dev/ttyN"
 
+#define cksum_trivial_usage \
+	"FILES..."
+#define cksum_full_usage \
+	"Calculates the CRC32 checksums of FILES."
+
 #define clear_trivial_usage \
 	""
 #define clear_full_usage \