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Diffstat (limited to 'reference/C/CONTRIB/SNIP/glbl_env.c')
| -rwxr-xr-x | reference/C/CONTRIB/SNIP/glbl_env.c | 364 |
1 files changed, 364 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/glbl_env.c b/reference/C/CONTRIB/SNIP/glbl_env.c new file mode 100755 index 0000000..9699aae --- /dev/null +++ b/reference/C/CONTRIB/SNIP/glbl_env.c @@ -0,0 +1,364 @@ +/*****************************************************************************
+ This code is based upon the program SETPATH.PAS (located in BPROGA) by
+ David Dubois [71401,747]
+
+ This Turbo C version is written by Peter Thomas [75716,2377]
+
+ This series of routines are designed to Locate, Retrieve, Update, and
+ Remove "Variables" from the MASTER copy of the DOS Environment table.
+ The routines have been written in a manner that avoids linking any
+ EXTERNAL routines for string manipulation, and thus should be independent
+ of memory model being used.
+
+ Be careful that changes made to the Environment with these routines
+ ONLY OCCUR IN THE MASTER COPY, and that if COMMAND.COM is spawned
+ from a routine that has changed the environment, NO CHANGES WILL BE
+ SEEN IN THE ENVIRONMENT. This is most apparent when this program is run
+ in the INTEGRATED environment: changes made by this technique will
+ not appear if the "OS Shell" is invoked, and will only appear on exit
+ from TC.
+
+ For full documentation on the techniques used here can be found in the
+ file COMENV.ARC located in LIB 2 of BPROGA on Compuserve.
+
+ As David Dubois says:
+
+ I hereby dedicate this knowledge to the public domain. Feel free to use
+ it, but if you do, please mention my name. There are no guarantees, and
+ in fact, I wouldn't bet a dollar that it will work every time.
+
+ That this works at all is based on experimental, rather than properly
+ documented, evidence. There are no guarantees. But then, its free.
+
+*****************************************************************************/
+
+#include <stdio.h>
+#include <dos.h>
+
+#ifdef __ZTC__
+ #error ZTC/C++ not supported - huge pointers required!
+#endif
+
+#ifdef __TURBOC__
+ #include <alloc.h>
+ #define Fmalloc farmalloc
+ #define Ffree farfree
+#else
+ #include <malloc.h>
+ #include <stdlib.h>
+ #define far _far
+ #define Fmalloc _fmalloc
+ #define Ffree _ffree
+ #define MK_FP(seg,offset) \
+ ((void far *)(((unsigned long)(seg)<<16) | (unsigned)(offset)))
+#endif
+
+/*
+ * Mstr_FindEnvironment:
+ * Scans for the "Master" Environment area, and returns
+ * a pointer to it, and the size of the environment.
+*/
+void Mstr_FindEnvironment ( char far **Env , unsigned *EnvSize )
+{
+ unsigned int far *CommandSeg, far *TempSeg ;
+ char far *BlockSeg ;
+
+ /*
+ * Scan through PSP's looking for a block that is its own father.
+ * This block is the PSP of COMMAND.COM
+ */
+ TempSeg = MK_FP ( _psp , 0 ) ;
+ do
+ {
+ CommandSeg = TempSeg ;
+ TempSeg = MK_FP ( *(TempSeg+8) , 0 ) ;
+ }
+ while ( TempSeg != CommandSeg ) ;
+
+ /*
+ * Scan forward through memory looking for the correct MSB.
+ * This will have COMMAND.COM's PSP as owner, and begin with
+ * the character M
+ */
+ BlockSeg = (char far *)CommandSeg ;
+ do
+ {
+ BlockSeg = MK_FP ( FP_SEG(BlockSeg)+1 , 0 ) ;
+ }
+ while ( ( *(unsigned int far *)(BlockSeg+1) != FP_SEG ( CommandSeg ) ) ||
+ ( *BlockSeg != 'M' ) ) ;
+
+ /*
+ * The environment is the NEXT segment of memory
+ * and bytes 4 and 5 are the size in paragraphs
+ */
+ *Env = MK_FP ( FP_SEG(BlockSeg)+1 , 0 ) ;
+ *EnvSize = 16 * *(unsigned int far *)(BlockSeg+3) ;
+}
+
+/*
+ * Mstr_getenv:
+ * Scans the "Master" Environment for a given "sub string"
+ * and returns a pointer to it.
+ * Similar to Turbo routine "getenv" but uses the Master copy of the
+ * environment table.
+*/
+char far *Mstr_getenv (char far *Env , char far *name)
+{
+ char far *Sub_Env, far *str1, far *str2 ;
+
+ /*
+ * Start at the beginning of the environment
+ */
+ Sub_Env = Env ;
+
+ /*
+ * While the "sub string" we're looking at is non-zero
+ */
+ for ( ; *Sub_Env ; )
+ {
+ /*
+ * Simulate a "strcmp" on the "sub string" of the environment
+ * and the string we're looking for
+ */
+ for ( str1 = Sub_Env , str2 = name ;
+ (*str1) && (*str2) && ( *str1 == *str2) ;
+ str1++ , str2++ ) ;
+ /*
+ * If we reached the end of the string we're looing for
+ * we've found the correct portion of the environment.
+ * Return the ptr to the start of this "sub string"
+ */
+ if ( !*str2 )
+ return ( Sub_Env ) ;
+
+ /*
+ * Otherwise, advance to the next "sub string" in the environment
+ * by performing a "strchr" function
+ */
+ for ( ; *(Sub_Env++) ; ) ;
+ }
+
+ /*
+ * Obviously, the string is not present in the environment.
+ * Return this fact.
+ */
+ return ( NULL ) ;
+}
+
+/*
+ * Mstr_delenv:
+ * Scans the "Master" Environment for a given "sub string"
+ * and removes it.
+*/
+int Mstr_delenv (char far *Env , unsigned EnvSize , char far *name)
+{
+ char far *Sub_Env , far *New_Env ;
+ char huge *Dest , far *Src , huge *End_Env ;
+
+ int Done ;
+ unsigned Ctr ;
+
+ /*
+ * Allocate a chunk of storage to act as a "working" copy of
+ * the Environment table
+ */
+ New_Env = Fmalloc ( EnvSize ) ;
+
+ /*
+ * Copy the data from the Master to Working copy of the
+ * Environment table.
+ * Simulates a "memcpy" function.
+ */
+ for ( Src = Env , Dest = (char far *)New_Env , Ctr = 0 ;
+ Ctr < EnvSize ;
+ *(Dest++) = *(Src++) , Ctr++ ) ;
+
+ /*
+ * Scan the working copy of the environment for the desired
+ * sub string
+ */
+ Sub_Env = Mstr_getenv ( New_Env , name ) ;
+
+ if ( Sub_Env == NULL )
+ {
+ /*
+ * If not found, do nothing
+ */
+ Done = -1 ;
+ } else {
+ /*
+ * Locate the end of the string to delete
+ * Simulate a "strchr" call
+ */
+ for ( Src = Sub_Env ; *(Src++) ; ) ;
+
+ /*
+ * Move the rest of the environment back over the "sub string"
+ * being deleted.
+ * Simulated "memcpy" function.
+ * Huge pointers used for pointer comparison purposes.
+ */
+ for ( Dest = (char huge *)Sub_Env , End_Env = (char huge *) (New_Env + EnvSize ) ;
+ ( Dest < End_Env ) ;
+ *(Dest++) = *(Src++) ) ;
+
+ /*
+ * Copy the data from the Working to Master copy of the
+ * Environment table.
+ * Simulates a "memcpy" function.
+ */
+ for ( Src = New_Env , Dest = (char huge *)Env , Ctr = 0 ;
+ Ctr < EnvSize ;
+ *(Dest++) = *(Src++) , Ctr++ ) ;
+
+ /*
+ * Signal all done
+ */
+ Done = 0 ;
+ }
+
+ /*
+ * Free all working storage
+ */
+ Ffree ( New_Env ) ;
+
+ return ( Done ) ;
+}
+
+/*
+ * Mstr_putenv:
+ * Adds/Replaces a given "sub string" in the Master Environment.
+ * Similar to Turbo routine "putenv" but uses the Master copy of the
+ * environment table.
+*/
+int Mstr_putenv (char far *Env , unsigned EnvSize , char far *name )
+{
+ char far *Sub_Env , far *Temp_Name ;
+ char huge *Dest , far *Src , huge *End_Env ;
+ int Done ;
+
+ /*
+ * Allocate a chunk of storage to create the Variable name to add
+ * to the Environment table
+ */
+ Temp_Name = Fmalloc ( 256 ) ;
+
+ /*
+ * Extract only the Name portion of the data to add to the Environment
+ */
+ for ( Src = name , Dest = Temp_Name ;
+ *Src && ( *Src != '=' ) ;
+ *(Dest++) = *(Src++) ) ;
+
+ /*
+ * Ensure that the resulting name is well formed.
+ */
+ *(Dest++) = '=' ;
+ *Dest = 0 ;
+
+ /*
+ * Delete this sub string if found in the environment
+ */
+ Mstr_delenv ( Env , EnvSize , Temp_Name ) ;
+
+ /*
+ * Locate the END of the Master table by locating a zero length
+ * String in it
+ */
+ Sub_Env = Env ;
+ for ( ; *Sub_Env ; )
+ {
+ for ( ; *(Sub_Env++) ; ) ;
+ }
+
+ /*
+ * Add the new string to the END of the existing environment, with
+ * trincation IF needed
+ */
+ for ( Dest = (char huge *)(Sub_Env) , Src = name , End_Env = (char huge *) (Env + EnvSize ) ;
+ ( Dest < End_Env ) && (*Src) ;
+ *(Dest++) = *(Src++) ) ;
+
+ Done = -1 ;
+ if ( !*Src )
+ {
+ /*
+ * If the string to add was FULLY added, ensure that the
+ * newly updated environment is properly finished
+ */
+ Done = 0 ;
+ *(Dest++) = 0 ;
+ *Dest = 0 ;
+ }
+
+ /*
+ * As a real safety measure, ensure that the FINAL two bytes of the
+ * Environment are both 0. This will finish the last string AND
+ * ensure that a zero length string is also present
+ */
+ *(End_Env-1) = 0 ;
+ *(End_Env-2) = 0 ;
+
+ /*
+ * Free all working storage
+ */
+ Ffree ( Temp_Name ) ;
+
+ return ( Done ) ;
+}
+
+void main(void)
+{
+ char far *Env ;
+ unsigned EnvSize ;
+
+ /*
+ * Locate the Master Table
+ */
+ Mstr_FindEnvironment ( &Env, &EnvSize ) ;
+
+ /*
+ * Describe what we've just found
+ */
+ printf ( "Env = %Fp Size = %u\n\n" , Env , EnvSize ) ;
+
+ /*
+ * Search for, and display LOCATIONS of PATH, FRED and BERT
+ */
+ printf ( "Search for PATH= returns %Fp\n", Mstr_getenv ( Env , "PATH=" ) ) ;
+ printf ( "Search for FRED= returns %Fp\n", Mstr_getenv ( Env , "FRED=" ) ) ;
+ printf ( "Search for BERT= returns %Fp\n", Mstr_getenv ( Env , "BERT=" ) ) ;
+
+ /*
+ * Add FRED and BERT to the environment
+ */
+ Mstr_putenv ( Env , EnvSize , "FRED=fred" ) ;
+ Mstr_putenv ( Env , EnvSize , "BERT=bert" ) ;
+
+ printf ( "\nAdded FRED and BERT to environment\n" ) ;
+
+ /*
+ * Search for, and display LOCATIONS of PATH ,FRED and BERT
+ */
+ printf ( "Search for PATH= returns %Fp\n", Mstr_getenv ( Env , "PATH=" ) ) ;
+ printf ( "Search for FRED= returns %Fp\n", Mstr_getenv ( Env , "FRED=" ) ) ;
+ printf ( "Search for BERT= returns %Fp\n", Mstr_getenv ( Env , "BERT=" ) ) ;
+
+ /*
+ * Delete FRED from the environment
+ */
+ Mstr_delenv ( Env , EnvSize , "FRED=" ) ;
+
+ printf ( "\nDeleted FRED= from the environment\n" ) ;
+
+ /*
+ * Search for, and display LOCATIONS of PATH, FRED, and BERT
+ */
+ printf ( "Search for PATH= returns %Fp\n", Mstr_getenv ( Env , "PATH=" ) ) ;
+ printf ( "Search for FRED= returns %Fp\n", Mstr_getenv ( Env , "FRED=" ) ) ;
+ printf ( "Search for BERT= returns %Fp\n", Mstr_getenv ( Env , "BERT=" ) ) ;
+
+ printf ( "\nIssue the DOS command SET and see that BERT is now set\n" ) ;
+
+}
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