From d13d8a046838ce3d0e2643bb5b49f2ff77d679ca Mon Sep 17 00:00:00 2001
From: Marc Horowitz <marc@mit.edu>
Date: Wed, 1 Nov 1989 20:02:01 +0000
Subject: Initial revision

---
 zwgc/substitute.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)
 create mode 100644 zwgc/substitute.c

(limited to 'zwgc/substitute.c')

diff --git a/zwgc/substitute.c b/zwgc/substitute.c
new file mode 100644
index 0000000..5372fef
--- /dev/null
+++ b/zwgc/substitute.c
@@ -0,0 +1,149 @@
+#include "new_memory.h"
+#include "lexer.h"
+#include "substitute.h"
+
+/*
+ *  Internal Routine:
+ *
+ *    string eat_dollar_sign_stuff(string (*lookup)(string); string *text_ptr)
+ *        Modifies: *text_ptr
+ *        Effects: This routine deals with handling the stuff after a '$'
+ *                 for substitute.  If *text_ptr starts with a valid
+ *                 variable reference (minus the leading '$'), we look up
+ *                 the variable using lookup and return its value.
+ *                 *text_ptr is also advanced past the variable reference.
+ *                 If a '$' starts *text_ptr, *text_ptr is advanced past it &
+ *                 "$" returned.  (This handles "$$" -> "$")  Otherwise,
+ *                 "$" is returned and *text_ptr is not advanced.
+ *                 The returned string must not be freed.
+ */
+
+static string eat_dollar_sign_stuff(lookup, text_ptr)
+     string (*lookup)();
+     string *text_ptr;                 /* Input/Output parameter */
+{
+    char c;
+    char closing_brace = 0;
+    char *p = *text_ptr;
+    char *variable_name_start;
+    int variable_name_length;
+
+    /*
+     * Handle "$$" -> "$" translation:
+     */
+    c = *p;
+    if (c=='$') {
+	*text_ptr = p+1;
+	return("$");
+    }
+
+    /*
+     * If opening brace present (i.e., '(' or '{'), skip it and save away
+     * what closing brace we must see at the end of the variable reference:
+     */
+    if (c=='{') {
+	closing_brace = '}';
+	c = *++p;
+    } else if (c=='(') {
+	closing_brace = ')';
+	c = *++p;
+    }
+
+    /*
+     * Eat {identifier_char}* keeping track of what we ate:
+     */
+    variable_name_start = p;
+    variable_name_length = 0;
+    while (c = *p, is_identifier_char(c)) {
+	p++;
+	variable_name_length++;
+    }
+
+    /*
+     * If there was an opening brace, there had better be a comparable
+     * closing brace.  If so, skip it.  If not, we have an invalid variable
+     * reference so return '$' without advancing *text_ptr.
+     */
+    if (closing_brace) {
+	if (c==closing_brace)
+	  c = *++p;
+	else
+	  return("$");
+    }
+
+    /*
+     * Zero length variable names are not valid:
+     */
+    if (!variable_name_length)
+      return("$");
+
+    /*
+     * We have a valid variable reference.  Advance past it then lookup
+     * its value and return it:
+     */
+    *text_ptr = p;
+    if (variable_name_length > MAX_IDENTIFIER_LENGTH)
+      variable_name_length = MAX_IDENTIFIER_LENGTH;
+    variable_name_start = string_CreateFromData(variable_name_start,
+						variable_name_length);
+    p = lookup(variable_name_start);
+    free(variable_name_start);
+    return(p);
+}
+
+/*
+ *    string substitute(string (*lookup)(string); string text)
+ *        Effects: returns the result of expanding all variable
+ *                 references in text using lookup.  Example:
+ *                 "test $foo.$bar baz" would be translated to
+ *                 "text <foo>.<bar> baz" where "<foo>" is the value of
+ *                 lookup("foo") and "<bar>" is the value of lookup("bar").
+ *                 Variables are case sensitive and have the form
+ *                 {identifier_char}+ where identifier_char is defined
+ *                 in lexer.h by is_identifier_char.  $(foo) and
+ *                 ${foo} are alternate forms for $foo.  In particular,
+ *                 ${foo}bar is a reference to foo followed by "bar" while
+ *                 $foobar is a reference to foobar.  Incomplete variable
+ *                 references like $(foo bar are displayed as if they
+ *                 were not variable references.  To allow quoting, "$$"
+ *                 is translated to "$".  Only the first
+ *                 MAX_IDENTIFIER_LENGTH characters of an identifier are
+ *                 significant.  The strings returned by lookup are not
+ *                 modified in any way or freed.
+ */
+
+string substitute(lookup, text)
+     string (*lookup)();
+     string text;
+{
+    string result_so_far = string_Copy("");
+    char *p, *temp;
+
+    for (;;) {
+	/*
+	 * Move [^$]* from start of text to end of result_so_far:
+	 */
+	for (p=text; *p && (*p)!='$'; p++) ;
+	if (text != p) {
+	    temp = string_CreateFromData(text, p-text);
+	    text = p;
+	    result_so_far = string_Concat2(result_so_far, temp);
+	    free(temp);
+	}
+
+	/*
+	 * If text now empty, exit -- the result is in result_so_far:
+	 */
+	if (!*text)
+	  return(result_so_far);
+
+	/*
+	 * Otherwise, text begins with a '$'.  Eat it then call
+	 * eat_dollar_sign_stuff to process stuff after it.
+	 * Append result to result_so_far, update text, & continue.
+	 */
+	text++;
+	p = eat_dollar_sign_stuff(lookup, &text);
+	result_so_far = string_Concat2(result_so_far, p);
+    }
+}
-- 
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