Fiddling with environment variables.

diff --git a/env.c b/env.c
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--- /dev/null
+++ b/env.c
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+/* -*-c-*-
+ *
+ * $Id: env.c,v 1.1 1999/07/26 23:15:57 mdw Exp $
+ *
+ * Fiddling with environment variables
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of the mLib utilities library.
+ *
+ * mLib is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * mLib is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with mLib; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: env.c,v $
+ * Revision 1.1  1999/07/26 23:15:57  mdw
+ * Fiddling with environment variables.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "alloc.h"
+#include "sym.h"
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct var {
+  sym_base _base;
+  char *v;
+} var;
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @env_get@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *             @const char *name@ = pointer to variable name to look up
+ *
+ * Returns:    Pointer to corresponding value string, or null.
+ *
+ * Use:                Looks up an environment variable in the table and returns its
+ *             value.  If the variable can't be found, a null pointer is
+ *             returned.
+ */
+
+char *env_get(sym_table *t, const char *name)
+{
+  var *e = sym_find(t, name, -1, 0, 0);
+  return (e ? e->v : 0);
+}
+
+/* --- @env_put@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *             @const char *name@ = pointer to variable name to set
+ *             @const char *value@ = pointer to value string to assign
+ *
+ * Returns:    ---
+ *
+ * Use:                Assigns a value to a variable.  If the @name@ contains an
+ *             equals character, then it's assumed to be of the form
+ *             `VAR=VALUE' and @value@ argument is ignored.  Otherwise, if
+ *             @value@ is null, the variable is deleted.  Finally, the
+ *             normal case: @name@ is a plain name, and @value@ is a normal
+ *             string causes the variable to be assigned the value in the
+ *             way you'd expect.
+ */
+
+void env_put(sym_table *t, const char *name, const char *value)
+{
+  char *q = 0;
+
+  /* --- Sort out the mess with `NAME=VALUE' forms --- */
+
+  {
+    size_t eq = strcspn(name, "=");
+    if (name[eq] == '=') {
+      q = xmalloc(eq + 1);
+      memcpy(q, name, eq);
+      q[eq] = 0;
+      value = name + eq + 1;
+      name = q;
+    }
+  }
+
+  /* --- Read the current value --- */
+
+  if (!value) {
+    var *v;
+    if ((v = sym_find(t, name, -1, 0, 0)) != 0) {
+      free(v->v);
+      sym_remove(t, v);
+    }
+  } else {
+    unsigned found;
+    var *v = sym_find(t, name, -1, sizeof(*v), &found);
+    if (found)
+      free(v->v);
+    v->v = xstrdup(value);
+  }
+
+  /* --- Tidying --- */
+
+  if (q)
+    free(q);
+}
+
+/* --- @env_import@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *             @char **env@ = pointer to an environment list
+ *
+ * Returns:    ---
+ *
+ * Use:                Inserts all of the environment variables listed into a symbol
+ *             table for rapid access.  Equivalent to a lot of calls to
+ *             @env_put@.
+ */
+
+void env_import(sym_table *t, char **env)
+{
+  while (*env) {
+    env_put(t, *env, 0);
+    env++;
+  }
+}
+
+/* --- @env_export@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *
+ * Returns:    A big environment list.
+ *
+ * Use:                Extracts an environment table from a symbol table
+ *             representation of an environment.  The table and all of the
+ *             strings are in one big block allocated from the heap.
+ */
+
+char **env_export(sym_table *t)
+{
+  size_t n = 1;
+  size_t sz = 0;
+  sym_iter i;
+  var *v;
+  char **env;
+  char *p, **pp;
+
+  /* --- Work out sizes for everything --- */
+
+  for (sym_mkiter(&i, t); (v = sym_next(&i)) != 0; ) {
+    n++;
+    sz += strlen(SYM_NAME(v)) + strlen(v->v) + 2;
+  }
+
+  /* --- Allocate the big chunk of memory --- */
+
+  env = pp = xmalloc(n * sizeof(char *) + sz);
+  p = (char *)(env + n);
+
+  /* --- Dump the output in the big chunk of memory --- */
+
+  for (sym_mkiter(&i, t); (v = sym_next(&i)) != 0; ) {
+    const char *name = SYM_NAME(v);
+    size_t nlen = strlen(name), vlen = strlen(v->v);
+    *pp++ = p;
+    memcpy(p, name, nlen); p += nlen;
+    *p++ = '=';
+    memcpy(p, v->v, vlen); p += vlen;
+    *p++ = 0;
+  }
+  *pp++ = 0;
+  return (env);
+}
+
+/* --- @env_destroy@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to symbol table
+ *
+ * Returns:    ---
+ *
+ * Use:                Destroys all the variables in the symbol table.
+ */
+
+void env_destroy(sym_table *t)
+{
+  sym_iter i;
+  var *v;
+
+  for (sym_mkiter(&i, t); (v = sym_next(&i)) != 0; )
+    free(v->v);
+  sym_destroy(t);
+}
+
+/*----- That's all, folks -------------------------------------------------*/

diff --git a/env.h b/env.h
new file mode 100644 (file)
index 0000000..efe4052
--- /dev/null
+++ b/env.h
@@ -0,0 +1,131 @@
+/* -*-c-*-
+ *
+ * $Id: env.h,v 1.1 1999/07/26 23:15:57 mdw Exp $
+ *
+ * Fiddling with environment variables
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of the mLib utilities library.
+ *
+ * mLib is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * mLib is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with mLib; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: env.h,v $
+ * Revision 1.1  1999/07/26 23:15:57  mdw
+ * Fiddling with environment variables.
+ *
+ */
+
+#ifndef ENV_H
+#define ENV_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#ifndef SYM_H
+#  include "sym.h"
+#endif
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @env_get@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *             @const char *name@ = pointer to variable name to look up
+ *
+ * Returns:    Pointer to corresponding value string, or null.
+ *
+ * Use:                Looks up an environment variable in the table and returns its
+ *             value.  If the variable can't be found, a null pointer is
+ *             returned.
+ */
+
+extern char *env_get(sym_table */*t*/, const char */*name*/);
+
+/* --- @env_put@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *             @const char *name@ = pointer to variable name to set
+ *             @const char *value@ = pointer to value string to assign
+ *
+ * Returns:    ---
+ *
+ * Use:                Assigns a value to a variable.  If the @name@ contains an
+ *             equals character, then it's assumed to be of the form
+ *             `VAR=VALUE' and @value@ argument is ignored.  Otherwise, if
+ *             @value@ is null, the variable is deleted.  Finally, the
+ *             normal case: @name@ is a plain name, and @value@ is a normal
+ *             string causes the variable to be assigned the value in the
+ *             way you'd expect.
+ */
+
+extern void env_put(sym_table */*t*/,
+                   const char */*name*/, const char */*value*/);
+
+/* --- @env_import@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *             @char **env@ = pointer to an environment list
+ *
+ * Returns:    ---
+ *
+ * Use:                Inserts all of the environment variables listed into a symbol
+ *             table for rapid access.  Equivalent to a lot of calls to
+ *             @env_put@.
+ */
+
+extern void env_import(sym_table */*t*/, char **/*env*/);
+
+/* --- @env_export@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to a symbol table
+ *
+ * Returns:    A big environment list.
+ *
+ * Use:                Extracts an environment table from a symbol table
+ *             representation of an environment.  The table and all of the
+ *             strings are in one big block allocated from the heap.
+ */
+
+extern char **env_export(sym_table */*t*/);
+
+/* --- @env_destroy@ --- *
+ *
+ * Arguments:  @sym_table *t@ = pointer to symbol table
+ *
+ * Returns:    ---
+ *
+ * Use:                Destroys all the variables in the symbol table.
+ */
+
+extern void env_destroy(sym_table */*t*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif

diff --git a/man/env.3 b/man/env.3
new file mode 100644 (file)
index 0000000..7894d7c
--- /dev/null
+++ b/man/env.3
@@ -0,0 +1,86 @@
+.\" -*-nroff-*-
+.TH env 3 "26 July 1999" mLib
+.SH "NAME"
+env \- efficient fiddline with environment variables
+.\" @env_get
+.\" @env_put
+.\" @env_import
+.\" @env_export
+.\" @env_destroy
+.SH "SYNOPSIS"
+.nf
+.B "#include <mLib/env.h>"
+
+.BI "char *env_get(sym_table *" t ", const char *" name );
+.BI "void env_put(sym_table * " t ,
+.BI "             const char *" name ", const char *" value );
+.BI "void env_import(sym_table *" t ", char **" env );
+.BI "char **env_export(sym_table *" t );
+.fi
+.SH "DESCRIPTION"
+The functions in the
+.B "<mLib/env.h>"
+header manipulate environment variables stored in a hash table.
+.PP
+The function
+.B env_import
+reads a standard Unix environment array and stores the variables in the
+symbol table.  (A standard Unix environment array is an array of
+pointers to strings of the form
+.IB name = value
+terminated by a null pointer.  This format is used for the global
+.B environ
+variable, and by the
+.BR execve (2)
+function.)  The symbol table must have already been created (see
+.BR sym_create (3)).
+.PP
+The function
+.B env_export
+creates a Unix environment array from a symbol table.  The environment
+array is one big block of memory allocated using
+.BR malloc (3);
+hence, one call to
+.BR free (3)
+releases all the memory used for the pointer array and the strings.
+.PP
+The
+.B env_get
+function looks up a variable in an environment symbol table.  The
+returned result is the variable's value if it exists, or a null pointer
+if not.
+.PP
+The
+.B env_put
+function sets or deletes environment variables.  If the
+.I name
+argument contains an
+.RB ` = '
+character, it is assumed to be of the form
+.IB n = v\fR;
+the
+.I value argument is ignored, and the variable
+.I n
+is assigned the value
+.IR v .
+Otherwise, if
+.I value
+is not a null pointer, the variable
+.I name
+is assigned the value
+.I value .
+Finally, if
+.I value
+is null, the variable
+.I name
+is deleted.
+.PP
+The
+.B env_destroy
+function frees all the memory used by an environment symbol table.  The
+table itself is destroyed too.
+.SH "SEE ALSO"
+.BR sym (3),
+.BR mLib (3).
+.SH "AUTHOR"
+Mark Wooding, <mdw@nsict.org>