0,0 → 1,113 |
/* |
* routines used to manipulate the environment block |
*/ |
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#include <i86.h> |
#include <string.h> |
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#include "env.h" |
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/* looks for varname in environment block and returns a far ptr to it if |
* found, NULL otherwise. varname MUST be in upper-case and MUST be terminated |
* by either a = sign or a NULL terminator */ |
char far *env_lookup(unsigned short env_seg, const char *varname) { |
char far *env = MK_FP(env_seg, 0); |
int i; |
for (;;) { |
/* is this it? */ |
for (i = 0;; i++) { |
if ((varname[i] == '=') || (varname[i] == 0)) { |
if (env[i] == '=') return(env); /* FOUND! */ |
break; /* else look for next string */ |
} |
if (varname[i] != env[i]) break; |
} |
/* move env to end of current string */ |
while (*env != 0) env++; |
/* if there's another trailing zero, then that is the end of environment */ |
env++; |
if (*env == 0) return(NULL); |
} |
} |
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/* returns the size, in bytes, of the allocated environment block */ |
unsigned short env_allocsz(unsigned short env_seg) { |
unsigned short far *mcbsz = MK_FP(env_seg - 1, 3); /* block size is a word at offset +3 in the MCB */ |
return(*mcbsz * 16); /* return size in bytes, not paragraphs */ |
} |
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/* remove a variable from environment, if present. returns 0 on success, non-zero if variable not found */ |
int env_dropvar(unsigned short env_seg, const char *varname) { |
unsigned short blocksz, traillen; |
unsigned short len; |
char far *varptr = env_lookup(env_seg, varname); |
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/* if variable not found in environment, quit now */ |
if (varptr == NULL) return(-1); |
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for (len = 0; varptr[len] != 0; len++); /* compute length of variable (without trailing null) */ |
blocksz = env_allocsz(env_seg); /* total environment size */ |
traillen = blocksz - (FP_OFF(varptr) + len + 1); /* how much bytes are present after the variable */ |
_fmemset(varptr, 0, len); /* zero out the variable */ |
if (traillen != 0) { |
_fmemmove(varptr, varptr + len + 1, traillen); /* move rest of memory */ |
} |
return(0); |
} |
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/* Writes a variable to environment block. The variable must in the form |
* "VARNAME=value". If variable is already present in the environment block, |
* then the value will be updated. If the new value is empty, then the |
* existing variable (if any) is removed. |
* VARNAME *MUST* be all-uppercase. |
* |
* This function returns: |
* ENV_SUCCESS = success |
* ENV_NOTENOM = not enough available space in memory block |
* ENV_INVSYNT = invalid syntax |
*/ |
int env_setvar(unsigned short env_seg, const char *v) { |
unsigned short envlen; |
unsigned short envfree; |
unsigned short vlen, veqpos; |
char far *env = MK_FP(env_seg, 0); |
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/* remove variable from environment, if already set */ |
env_dropvar(env_seg, v); |
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/* compute v length and find the position of the eq sign */ |
veqpos = 0xffff; |
for (vlen = 0; v[vlen] != 0; vlen++) { |
if (v[vlen] == '=') { |
if (veqpos != 0xffff) return(ENV_INVSYNT); /* equal sign is forbidden in value */ |
veqpos = vlen; |
} |
} |
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/* if variable empty, stop here */ |
if (veqpos == vlen - 1) return(ENV_SUCCESS); |
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/* compute current size of the environment */ |
for (envlen = 0; env[envlen] != 0; envlen++) { |
while (env[envlen] != 0) envlen++; /* consume a string */ |
} |
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/* compute free space available in environment */ |
envfree = env_allocsz(env_seg); |
envfree -= envlen; |
envfree -= 1; /* 1 byte for the environment's NULL terminator */ |
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/* do I have enough env space for the new var? */ |
if (envfree < vlen + 1) return(ENV_NOTENOM); |
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/* write the new variable (with its NULL terminator) to environment tail */ |
_fmemcpy(env + envlen, v, vlen + 1); |
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/* add the environment's NULL terminator */ |
env[envlen + vlen + 1] = 0; |
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return(ENV_SUCCESS); |
} |