Category : C Source Code
Archive   : E_C_STR.ZIP
Filename : ASCII.H

/* File : strings.d/ascii.h
Author : Richard A. O'Keefe
Updated: 28 April 1984
Purpose: Define Ascii mnemonics.

This file defines the ASCII control characters. Note that these
names refer to their use in communication; it is an ERROR to use
these names to talk about keyboard commands. For example, DO NOT
use EOT when you mean "end of file", as many people prefer ^Z (if
the Ascii code were taken seriously, EOT would log you off and
hang up the line as well). Similarly, DO NOT use DEL when you
mean "interrupt", many people prefer ^C. When writing a screen
editor, you should speak of tocntrl('C') rather than ETX (see the
header file "ctypes.h").
*/

#define NUL '\000' /* null character */
#define SOH '\001' /* Start Of Heading, start of message */
#define STX '\002' /* Start Of Text, end of address */
#define ETX '\003' /* End of TeXt, end of message */
#define EOT '\004' /* End Of Transmission */
#define ENQ '\005' /* ENQuiry "who are you" */
#define ACK '\006' /* (positive) ACKnowledge */
#define BEL '\007' /* ring the BELl */
#define BS '\010' /* BackSpace */
#define HT '\011' /* Horizontal Tab */
#define TAB '\011' /* an unofficial name for HT */
#define LF '\012' /* Line Feed (does not imply cr) */
#define NL '\012' /* unix unofficial name for LF: new line */
#define VT '\013' /* Vertical Tab */
#define FF '\014' /* Form Feed (new page starts AFTER this) */
#define CR '\015' /* Carriage Return */
#define SO '\016' /* Shift Out; select alternate character set */
#define SI '\017' /* Shift In; select ASCII again */
#define DLE '\020' /* Data Link Escape */
#define DC1 '\021' /* Device Control 1 */
#define XON '\021' /* transmitter on, resume output */
#define DC2 '\022' /* Device Control 2 (auxiliary on) */
#define DC3 '\023' /* Device Control 3 */
#define XOFF '\023' /* transmitter off, suspend output */
#define DC4 '\024' /* Device Control 4 (auxiliary off) */
#define NAK '\025' /* Negative AcKnowledge (signal error) */
#define SYN '\026' /* SYNchronous idle */
#define ETB '\027' /* End of Transmission Block, logical end of medium */
#define CAN '\030' /* CANcel */
#define EM '\031' /* End of Medium */
#define SUB '\032' /* SUBstitute */
#define ESC '\033' /* ESCape */
#define FS '\034' /* File Separator */
#define GS '\035' /* Group Separator */
#define RS '\036' /* Record Separator */
#define US '\037' /* Unit Separator */
#define SP '\040' /* SPace */
#define DEL '\177' /* DELete, rubout */
SHAR_EOF
sed 's/^X//' << 'SHAR_EOF' > bcmp.c
/* File : bcmp.c
Author : Richard A. O'Keefe.
Updated: 23 April 1984
Defines: bcmp()

bcmp(s1, s2, len) returns 0 if the "len" bytes starting at "s1" are
identical to the "len" bytes starting at "s2", non-zero if they are
different. The 4.2bsd manual page doesn't say what non-zero value
is returned, though the BUGS note says that it takes its parameters
backwards from strcmp. This suggests that it is something like
for (; --len >= 0; s1++, s2++)
if (*s1 != *s2) return *s2-*s1;
return 0;
There, I've told you how to do it. As the manual page doesn't come
out and *say* that this is the result, I tried to figure out what a
useful result might be. (I'd forgotten than strncmp stops when it
hits a NUL, which the above does not do.) What I came up with was:
the result is the number of bytes in the differing tails. That is,
after you've skipped the equal parts, how many characters are left?
To put it another way, N-bcmp(s1,s2,N) is the number of equal bytes
(the size of the common prefix). After deciding on this definition
I discovered that the CMPC3 instruction does exactly what I wanted.
The code assumes that N is non-negative.

Note: the "b" routines are there to exploit certain VAX order codes,
but the CMPC3 instruction will only test 65535 characters. The asm
code is presented for your interest and amusement.
*/

#include "strings.h"

#if VaxAsm

int bcmp(s1, s2, len)
char *s1, *s2;
int len;
{
asm("cmpc3 12(ap),*4(ap),*8(ap)");
}

#else ~VaxAsm

int bcmp(s1, s2, len)
register char *s1, *s2;
register int len;
{
while (--len >= 0 && *s1++ == *s2++) ;
return len+1;
}

#endif VaxAsm