| 0,0 → 1,113 |
|---|
| /* |
| * routines used to manipulate the environment block |
| */ |
| |
| #include <i86.h> |
| #include <string.h> |
| |
| #include "env.h" |
| |
| /* 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); |
| } |
| } |
| |
| |
| /* 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 */ |
| } |
| |
| |
| /* 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); |
| |
| /* if variable not found in environment, quit now */ |
| if (varptr == NULL) return(-1); |
| |
| 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); |
| } |
| |
| |
| /* 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); |
| |
| /* remove variable from environment, if already set */ |
| env_dropvar(env_seg, v); |
| |
| /* 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; |
| } |
| } |
| |
| /* if variable empty, stop here */ |
| if (veqpos == vlen - 1) return(ENV_SUCCESS); |
| |
| /* compute current size of the environment */ |
| for (envlen = 0; env[envlen] != 0; envlen++) { |
| while (env[envlen] != 0) envlen++; /* consume a string */ |
| } |
| |
| /* compute free space available in environment */ |
| envfree = env_allocsz(env_seg); |
| envfree -= envlen; |
| envfree -= 1; /* 1 byte for the environment's NULL terminator */ |
| |
| /* do I have enough env space for the new var? */ |
| if (envfree < vlen + 1) return(ENV_NOTENOM); |
| |
| /* write the new variable (with its NULL terminator) to environment tail */ |
| _fmemcpy(env + envlen, v, vlen + 1); |
| |
| /* add the environment's NULL terminator */ |
| env[envlen + vlen + 1] = 0; |
| |
| return(ENV_SUCCESS); |
| } |