diff options
Diffstat (limited to 'reference/C/CONTRIB/SNIP/mcb_env.c')
| -rwxr-xr-x | reference/C/CONTRIB/SNIP/mcb_env.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/mcb_env.c b/reference/C/CONTRIB/SNIP/mcb_env.c new file mode 100755 index 0000000..3fc4e3e --- /dev/null +++ b/reference/C/CONTRIB/SNIP/mcb_env.c @@ -0,0 +1,166 @@ +#include <stdio.h>
+#include <dos.h>
+#include <string.h>
+#include <ctype.h>
+
+#ifdef __TURBOC__
+ #include <alloc.h>
+ #define FAR far
+#else
+ #include <stdlib.h>
+ #define FAR _far
+#endif
+
+#if !defined(MK_FP)
+ #define MK_FP(seg,off) ((void FAR *)(((long)(seg) << 16)|(unsigned)(off)))
+#endif
+
+struct EnvRec {
+ unsigned EnvSeg; /*Segment of the environment*/
+ unsigned EnvLen; /*Usable length of the environment*/
+ } EnvRec;
+
+struct EnvRec *MasterEnv(void)
+{
+ unsigned owner;
+ unsigned mcb;
+ unsigned eseg;
+ static struct EnvRec env;
+
+ env.EnvSeg = env.EnvLen = 0;
+ owner = * ((unsigned FAR *) MK_FP(0, (2+4*0x2e)));
+
+ /* int 0x2e points to command.com */
+
+ mcb = owner -1;
+
+ /*Mcb points to memory control block for COMMAND */
+
+ if ( (*((char FAR *) MK_FP(mcb, 0)) != 'M') &&
+ (*((unsigned FAR *) MK_FP(mcb, 1)) != owner) )
+ return (struct EnvRec *) 0;
+
+ eseg = *((unsigned FAR *) MK_FP(owner, 0x2c));
+
+ /* Read segment of environment from PSP of COMMAND} */
+ /* Earlier versions of DOS don't store environment segment there */
+
+ if ( !eseg )
+ {
+
+ /* Master environment is next block past COMMAND */
+
+ mcb = owner + *((unsigned FAR *) MK_FP(mcb, 3));
+ if ( (*((char FAR *) MK_FP(mcb, 0)) != 'M') &&
+ (*((unsigned FAR *) MK_FP(mcb, 1)) != owner) )
+ return (struct EnvRec *) 0;
+ eseg = mcb + 1;
+ }
+ else mcb = eseg-1;
+
+ /* Return segment and length of environment */
+
+ env.EnvSeg = eseg;
+ env.EnvLen = *((unsigned FAR *) MK_FP(mcb, 3)) << 4 ;
+ return &env;
+}
+
+/*
+** Then a function to find the string to be replaced. This one'll
+** return a pointer to the string, or a pointer to the first (of 2)
+** NUL byte at the end of the environment.
+*/
+
+char FAR *SearchEnv( char FAR *eptr, char *search )
+{
+ char FAR *e;
+ char *s;
+ while ( *eptr )
+ {
+ for ( s=search, e=eptr; *e && *s && (*e == *s); e++, s++ )
+ ; /* NULL STATEMENT */
+ if ( !*s )
+ break;
+ while ( *eptr )
+ eptr++; /* position to the NUL byte */
+ eptr++; /* next string */
+ }
+ return eptr;
+}
+
+/*
+** Now, the function to replace, add or delete. If a value is not
+** given, the string is deleted.
+*/
+
+int SetEnvStr( struct EnvRec *env, char *search, char *value )
+{
+ /* -Set environment string, returning true if successful */
+
+ char FAR *envptr;
+ register char FAR *p;
+ char *s;
+ int newlen;
+ int oldlen;
+ int i;
+
+ if ( !env->EnvSeg || !search )
+ return 0;
+
+ /* get some memory for complete environment string */
+
+ newlen = strlen(search) + sizeof((char) '\0') + strlen(value) + 2;
+ if ( (s = (char *) malloc( newlen)) == NULL )
+ return 0;
+ for ( i = 0; *search; search++, i++ )
+ s[i] = *search;
+ s[i++] = '=';
+ s[i] = '\0';
+ envptr = SearchEnv((char FAR *) MK_FP(env->EnvSeg, 0), s );
+ if ( *envptr )
+ {
+ for ( p = envptr, oldlen = 0; *p; oldlen++, p++ )
+ ; /* can't use strlen() because of far pointer */
+ } /* will set p to point to terminating NUL */
+
+ if ( *value && (newlen > (int)env->EnvLen) ) /* not a deletion */
+ {
+ free( s );
+ return 0; /* won't fit */
+ }
+
+ if ( *envptr ) /* shift it down */
+ {
+ for ( ++p; (*p || *(p+1)); envptr++, p++ )
+ *envptr = *p;
+ *envptr++ = '\0';
+ *envptr = '\0';
+ }
+ if ( *value ) /* append it */
+ {
+ strcat(s, value);
+ while ( *s )
+ *(envptr++) = *s++;
+ *envptr++ = '\0';
+ *envptr = '\0';
+ }
+ free(s);
+ return 1;
+}
+
+/*
+** Ok, just to show you that I tested it :
+*/
+
+void main(void)
+{
+ char vn[80];
+ char va[80];
+ struct EnvRec *p = MasterEnv();
+
+ puts("enter variable name:");
+ gets(vn);
+ puts("enter value:");
+ gets(va);
+ printf("SetEnvStr returned %d\n", SetEnvStr( p, strupr(vn), va) );
+}
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