Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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c/its/lib/stdio/scanf.c
There are 9 other files named scanf.c in the archive. Click here to see a list.
/*
* SCANF - parses formatted input text
*
* Copyright (C) 1986 by Ian Macky, SRI International
*
* this scanf code conforms with the description of [f,s]scanf
* as described in Harbison & Steele's "C: A Reference Manual",
* sections 11.5.28 (scanf), 11.5.16 (fscanf) and 11.5.30 (sscanf)
*/
#include "stdio.h"
#include "ctype.h"
#include "varargs.h"
struct scanf_work {
int count; /* number of successful assignments */
FILE *stream; /* input stream (source) */
va_list args; /* pointer to arg list */
char *format; /* pointer to format string */
int assign; /* TRUE if assigning results from this parse */
int width; /* maximum field width */
int size; /* SHORT, LONG or NORMAL */
int error; /* flag set by parse routines if bad input */
};
#define CHAR_SET_SIZE 128 /* size of character set */
static int valid_char[CHAR_SET_SIZE];
/* first arg to duo_scanf() is this flag saying whether to read a signed
or unsigned value */
#define SIGNED 1
#define UNSIGNED 0
/* sf.size says what size object you want the return value to be stored
as. internally the largest size is used, which is then cast into
the requested size for storing */
#define SHORT -1
#define NORMAL 0
#define LONG 1
#ifndef TRUE
#define TRUE 1
#define FALSE 0
#endif
int sscanf(s, format, va_alist)
char *s, *format;
va_dcl /* note no semicolon! */
{
FILE *f;
va_list vargp;
int result;
va_start(vargp); /* set up pointer to args */
f = sopen(s, "r", strlen(s)); /* set up to read from string */
result = _fscanf(f, format, &vargp);
fclose(f); /* nuke the string FD */
return result;
}
int scanf(format, va_alist)
char *format;
va_dcl /* note no semicolon! */
{
va_list vargp;
va_start(vargp);
return _fscanf(stdin, format, &vargp);
}
int fscanf(stream, format, va_alist)
FILE *stream;
char *format;
va_dcl /* note no semicolon! */
{
va_list vargp;
va_start(vargp);
return _fscanf(stream, format, &vargp);
}
static int _fscanf(stream, format, args)
FILE *stream;
char *format;
va_list *args;
{
void duo_scanf(), c_scanf(), s_scanf(), x_scanf(), f_scanf();
void bracket_scanf();
struct scanf_work sf;
int c;
if (!_readable(stream)) return 0;
sf.stream = stream; /* put args 'n' stuff into global storage */
sf.args = *args; /* so subroutines can get at them */
sf.format = format;
sf.count = 0; /* number of successful parse&assigns */
/*
* it's more efficient for this PDP-10 CPU to do pre-increment
* char fetch operations, so we're going to make less elegant C
* code which will produce more efficient machine code. so sue me.
*/
c = *sf.format; /* start with first character */
while (c) {
/*
* whitespace in the format string means to skip over whitespace
* in the input stream, if any exists. any amount of format
* whitespace is semantically equivalent, so skip it all.
*/
if (isspace(c)) {
while (isspace(c = getc(sf.stream))) ;
if (c == EOF) break;
ungetc(c, sf.stream);
while (isspace(c = *++sf.format)) ;
continue;
}
/*
* a percent starts a conversion specification. if the next char is
* '*', then no assignment is done, the object is just parsed and
* skipped over. there may be a maximum field width, expressed as an
* unsigned decimal number, which must be positive. there may be a
* size specification, one of 'h' for short or 'l' (lowercase 'L') for
* long. all of those are optional, but if any appear, they must be
* in the order above. the required part is the conversion op, a single
* character, one of:
*
* c one or more characters
* d signed decimal
* e, E, f, g, G signed decimal floating-point
* o unsigned octal
* s whitespace-delimited string
* u unsigned decimal
* x, X unsigned hexidecimal
* % single percent-sign
* [ complicated string-scanner frob ]
*/
else if (c == '%') {
/*
* check for assignment flag.
*/
if ((c = *++sf.format) != '*')
sf.assign = TRUE;
else {
sf.assign = FALSE;
c = *++sf.format;
}
/*
* check for maximum field width specification. must be positive,
* if given (can't be negative, since the syntax doesn't allow a
* way to denote it)
*/
if (isdigit(c)) {
sf.width = c - '0';
while (isdigit(c = *++sf.format))
sf.width = sf.width * 10 + c - '0';
if (!sf.width) break; /* has to be positive */
} else sf.width = -1; /* -1 means unspecified */
/*
* now check for a size specification, 'h' for short, 'l' (lowercase
* 'L') for long, nothing for normal.
*/
switch (c) {
case 'h': sf.size = SHORT; c = *++sf.format; break;
case 'l': sf.size = LONG; c = *++sf.format; break;
default: sf.size = NORMAL;
}
/*
* now find out what it is they really want to do. each routine
* clears sf.error if its parse succeeds. for an unknown op,
* the error flag remains set, so the code falls out the bottom
* of the switch.
*/
sf.error = TRUE; /* initialize error-on-parse flag */
switch (c) {
case 'd': /* signed decimal */
duo_scanf(&sf, SIGNED, /* base = */ 10); break;
case 'u': /* unsigned decimal */
duo_scanf(&sf, UNSIGNED, 10); break;
case 'o': /* unsigned octal */
duo_scanf(&sf, UNSIGNED, 8); break;
case 'x': case 'X': /* unsigned hex */
x_scanf(&sf); break;
case 'c': /* character(s) */
c_scanf(&sf); break;
case 's': /* string */
s_scanf(&sf); break;
case 'f': case 'e': case 'E': case 'g': case 'G':
f_scanf(&sf); break; /* signed float */
case '%':
sf.error = ((c = getc(sf.stream)) != '%'); break;
case '[': /* complex frob ] */
bracket_scanf(&sf); break;
} /* if there was an error in */
if (sf.error) break; /* that parse, punt now. */
}
/*
* if it's not whitespace or a conversion op, then it's just joe
* random character, which must match what comes next in the input
* stream
*/
else if (c != getc(sf.stream)) {
ungetc(c, sf.stream);
break; /* break out of major while loop */
}
c = *++sf.format; /* get next char for while loop */
}
va_end(sf.args); /* wrap up? (placeholder i guess) */
if (!sf.count && feof(sf.stream)) /* if got EOF before making any */
return EOF; /* assignments, return EOF, else */
else return sf.count; /* return # of successful assigns */
}
/*
* scanner for 'd' (signed decimal), 'u' (unsigned decimal), and
* 'o' (unsigned octal). takes an int flag as arg1 saying if this
* parse is signed or not, and arg2 as the number base
*/
static void duo_scanf(sf, signflag, base)
int signflag, base;
struct scanf_work *sf;
{
long value = 0; /* where the value will accumulate */
int negate = FALSE; /* TRUE if should negate value */
int c;
while ((c = getc(sf->stream)) != EOF && isspace(c)) ; /* skip whitespace */
if (signflag) switch (c) {
case '-': negate = TRUE; /* fall into '+' code */
case '+': if (--sf->width) c = getc(sf->stream);
}
while (c != EOF && sf->width) {
if (isdigit(c)) {
value = value * base + c - '0';
sf->error = FALSE; /* got some digits, so OK # by me */
if (--sf->width) c = getc(sf->stream);
} else {
ungetc(c, sf->stream);
break;
}
}
if (sf->error) return;
if (sf->assign) {
sf->count++; /* bump successful assignment count */
if (negate) value = -value; /* take care of that unary minus */
switch (sf->size) { /* assign to the right type now... */
case SHORT:
*va_arg(sf->args, short *) = (short) value; break;
case NORMAL:
*va_arg(sf->args, int *) = (int) value; break;
case LONG:
*va_arg(sf->args, long *) = (long) value; break;
}
}
}
/*
* hexidecimal scanner
*/
static void x_scanf(sf)
struct scanf_work *sf;
{
long value = 0;
int c;
while ((c = getc(sf->stream)) != EOF && isspace(c)) ; /* skip whitespace */
if (c == '0') { /* ignore leading "0x" but count */
sf->error = FALSE; /* towards maximum field width */
if (--sf->width && ((c = getc(sf->stream)) == 'x' || c == 'X')) {
c = getc(sf->stream);
sf->width--;
}
}
while (c != EOF && sf->width) {
if (isxdigit(c)) {
sf->error = FALSE;
value *= 16;
if (isdigit(c)) value += (c - '0');
else value += ((c & ~040) - 'A' + 10);
if (--sf->width) c = getc(sf->stream);
} else {
ungetc(c, sf->stream);
break;
}
}
if (sf->error) return;
if (sf->assign) {
sf->count++; /* bump successful assignment count */
switch (sf->size) {
case SHORT:
*va_arg(sf->args, short *)= (short) value; break;
case NORMAL:
*va_arg(sf->args, int *) = (int) value; break;
case LONG:
*va_arg(sf->args, long *) = (long) value; break;
}
}
}
/*
* floating-point scanner; this would be nice nicer as separate
* steps; get a sign, get some digits, maybe a dot, maybe more
* digits, then maybe an e, maybe a sign, etc etc etc, but having
* to track the field width makes it a bitch, so for now i'm
* resorting to a single get-char loop with flags saying what
* field we're in, so there's a single place to watch the total
* # characters read so far... (but there must be a better way)
*/
static void f_scanf(sf)
struct scanf_work *sf;
{
double value, multiplier;
int exponent, negate, exp_neg, post_dot, in_exponent, c;
negate = exp_neg = post_dot = in_exponent = FALSE;
exponent = value = 0;
while ((c = getc(sf->stream)) != EOF && isspace(c)) ; /* skip whitespace */
switch (c) {
case '-': negate = TRUE; /* fall into '+' code */
case '+': if (--sf->width) c = getc(sf->stream);
}
while (c != EOF && sf->width) {
if (isdigit(c)) {
sf->error = FALSE;
if (in_exponent) exponent = exponent * 10 + c - '0';
else if (post_dot) value += (c - '0') / (multiplier *= 10.0);
else value = value * 10.0 + c - '0';
} else if (!post_dot && c == '.') {
post_dot = TRUE;
multiplier = 1.0;
} else if (!in_exponent && (c == 'e' || c == 'E')) {
in_exponent = TRUE;
if (--sf->width) switch (c = getc(sf->stream)) {
case '-': exp_neg = TRUE; /* fall into '+' code */
case '+': c = getc(sf->stream);
default: continue; /* don't get another char */
}
} else {
ungetc(c, sf->stream);
break;
}
if (--sf->width) c = getc(sf->stream);
}
if (sf->error) return;
for (; exponent > 0; exponent--) {
if (exp_neg) value /= 10.0;
else value *= 10.0;
}
if (sf->assign) {
sf->count++; /* bump successful assignment count */
if (negate) value = -value;
switch (sf->size) {
case LONG:
*((double *) va_arg(sf->args, double *)) = (double) value;
break;
default:
*((float *) va_arg(sf->args, float *)) = (float) value;
break;
}
}
}
/*
* character scanner
*/
static void c_scanf(sf)
struct scanf_work *sf;
{
int c;
char *s;
if (sf->width < 0) {
if ((c = getc(sf->stream)) != EOF) {
sf->error = FALSE;
if (sf->assign) {
*((int *) va_arg(sf->args, int)) = c;
sf->count++;
}
}
} else {
if (sf->assign) /* make a pointer to their array */
s = va_arg(sf->args, char *);
while (sf->width-- && (c = getc(sf->stream)) != EOF)
if (sf->assign) *s++ = c; /* suck the chars */
if (sf->width < 0) { /* if scanned everything they */
sf->error = FALSE; /* flag that parse was OK */
if (sf->assign) sf->count++;
}
}
}
/*
* string scanner
*/
static void s_scanf(sf)
struct scanf_work *sf;
{
int c;
char *s;
while ((c = getc(sf->stream)) != EOF && isspace(c)) ; /* skip whitespace */
if (sf->assign)
s = va_arg(sf->args, char *);
while (c != EOF && sf->width) {
if (!isspace(c)) {
if (sf->assign) *s++ = c;
sf->error = FALSE;
if (--sf->width) c = getc(sf->stream);
} else {
ungetc(c, sf->stream);
break;
}
}
if (sf->error) return;
if (sf->assign) {
*s = '\0';
sf->count++;
}
}
static void bracket_scanf(sf)
struct scanf_work *sf;
{
int c, i, logic;
char *s;
if ((c = *++sf->format) == '^') {
logic = FALSE;
c = *++sf->format;
} else if (c) /* must be SOMETHING */
logic = TRUE;
else return;
for (i = 0; i < CHAR_SET_SIZE; i++) /* initialize the screen */
valid_char[i] = !logic;
while (c != ']') {
valid_char[c] = logic;
if (!(c = *++sf->format)) return;
}
s = va_arg(sf->args, char *); /* point to destination buf */
while (sf->width-- && (c = getc(sf->stream)) != EOF) {
if (valid_char[c]) {
if (sf->assign) *s++ = c;
} else {
ungetc(c, sf->stream);
break;
}
}
sf->error = FALSE; /* null strings and everything A-OK */
if (sf->assign) {
*s = '\0';
sf->count++;
}
}