common: New function substitute_envvars.

* common/stringhelp.c (substitute_envvars): New.  Based on code in
gpg-connect-agent.
* common/t-stringhelp.c: Include sysutils.h.
(test_substitute_envvars): New.
--

GnuPG-bug-id: 5599

common/stringhelp.c

@@ -1692,3 +1692,107 @@ format_text (const char *text_in, int target_cols, int max_cols)
 
   return text;
 }
+
+
+/* Substitute environment variables in STRING and return a new string.
+ * On error the function returns NULL.  */
+char *
+substitute_envvars (const char *string)
+{
+  char *line, *p, *pend;
+  const char *value;
+  size_t valuelen, n;
+  char *result = NULL;
+
+  result = line = xtrystrdup (string);
+  if (!result)
+    return NULL; /* Ooops */
+
+  while (*line)
+    {
+      p = strchr (line, '$');
+      if (!p)
+        goto leave; /* No or no more variables.  */
+
+      if (p[1] == '$') /* Escaped dollar sign. */
+        {
+          memmove (p, p+1, strlen (p+1)+1);
+          line = p + 1;
+          continue;
+        }
+
+      if (p[1] == '{')
+        {
+          int count = 0;
+
+          for (pend=p+2; *pend; pend++)
+            {
+              if (*pend == '{')
+                count++;
+              else if (*pend == '}')
+                {
+                  if (--count < 0)
+                    break;
+                }
+            }
+          if (!*pend)
+            goto leave; /* Unclosed - don't substitute.  */
+        }
+      else
+        {
+          for (pend = p+1; *pend && (alnump (pend) || *pend == '_'); pend++)
+            ;
+        }
+
+      if (p[1] == '{' && *pend == '}')
+        {
+          int save = *pend;
+          *pend = 0;
+          value = getenv (p+2);
+          *pend++ = save;
+        }
+      else
+        {
+          int save = *pend;
+          *pend = 0;
+          value = getenv (p+1);
+          *pend = save;
+        }
+
+      if (!value)
+        value = "";
+      valuelen = strlen (value);
+      if (valuelen <= pend - p)
+        {
+          memcpy (p, value, valuelen);
+          p += valuelen;
+          n = pend - p;
+          if (n)
+            memmove (p, p+n, strlen (p+n)+1);
+          line = p;
+        }
+      else
+        {
+          char *src = result;
+          char *dst;
+
+          dst = xtrymalloc (strlen (src) + valuelen + 1);
+          if (!dst)
+            {
+              xfree (result);
+              return NULL;
+            }
+          n = p - src;
+          memcpy (dst, src, n);
+          memcpy (dst + n, value, valuelen);
+          n += valuelen;
+          strcpy (dst + n, pend);
+          line = dst + n;
+          xfree (result);
+          result = dst;
+        }
+    }
+
+ leave:
+  return result;
+}

common/stringhelp.h

@@ -166,6 +166,9 @@ int compare_version_strings (const char *my_version, const char *req_version);
 /* Format a string so that it fits within about TARGET_COLS columns.  */
 char *format_text (const char *text, int target_cols, int max_cols);
 
+/* Substitute environmen variabales in STRING.  */
+char *substitute_envvars (const char *string);
+
 
 /*-- mapstrings.c --*/
 const char *map_static_macro_string (const char *string);

common/t-stringhelp.c

@@ -43,6 +43,7 @@
 #include <limits.h>
 
 #include "t-support.h"
+#include "sysutils.h"
 #include "stringhelp.h"
 
 
@@ -1194,6 +1195,103 @@ test_compare_version_strings (void)
 }
 
 
+static void
+test_substitute_envvars (void)
+{
+  struct {
+    const char *name;
+    const char *value;
+  } envvars[] = {
+    { "HOME", "/home/joe" },
+    { "AVAR",  "avar" },
+    { "AVAR1", "avarx" },
+    { "AVAR2", "avarxy" },
+    { "AVAR3", "avarxyz" },
+    { "AVAR0", "ava" },
+    { "MY_VAR", "my_vars_value" },
+    { "STRANGE{X}VAR", "strange{x}vars-value" },
+    { "ZERO",  "" }
+  };
+  struct {
+    const char *string;
+    const char *result;
+  } tests[] = {
+    { "foo bar",
+      "foo bar"
+    },
+    { "foo $HOME",
+      "foo /home/joe"
+    },
+    { "foo $HOME ",
+      "foo /home/joe "
+    },
+    { "foo $HOME$$",
+      "foo /home/joe$"
+    },
+    { "foo ${HOME}/.ssh",
+      "foo /home/joe/.ssh"
+    },
+    { "foo $HOME/.ssh",
+      "foo /home/joe/.ssh"
+    },
+    { "foo $HOME_/.ssh",
+      "foo /.ssh"
+    },
+    { "foo $HOME/.ssh/$MY_VAR:1",
+      "foo /home/joe/.ssh/my_vars_value:1"
+    },
+    { "foo $HOME${MY_VAR}:1",
+      "foo /home/joemy_vars_value:1"
+    },
+    { "${STRANGE{X}VAR}-bla",
+      "strange{x}vars-value-bla"
+    },
+    { "${STRANGE{X}{VAR}-bla", /* missing "}" */
+      "${STRANGE{X}{VAR}-bla"
+    },
+    { "zero->$ZERO<-",
+      "zero-><-"
+    },
+    { "->$AVAR.$AVAR1.$AVAR2.$AVAR3.$AVAR0<-",
+      "->avar.avarx.avarxy.avarxyz.ava<-"
+    },
+    { "",
+      ""
+    }
+  };
+  int idx;
+  char *res;
+
+  for (idx=0; idx < DIM(envvars); idx++)
+    if (gnupg_setenv (envvars[idx].name, envvars[idx].value, 1))
+      {
+        fprintf (stderr,"error setting envvar '%s' to '%s': %s\n",
+                 envvars[idx].name, envvars[idx].value,
+                 strerror (errno));
+        exit (2);
+      }
+
+  for (idx=0; idx < DIM(tests); idx++)
+    {
+      res = substitute_envvars (tests[idx].string);
+      if (!res)
+        {
+          fprintf (stderr,"error substituting '%s' (test %d): %s\n",
+                   tests[idx].string, idx, strerror (errno));
+          exit (2);
+        }
+      if (strcmp (res, tests[idx].result))
+        {
+          fprintf (stderr, "substituted '%s'\n", tests[idx].string);
+          fprintf (stderr, "     wanted '%s'\n", tests[idx].result);
+          fprintf (stderr, "        got '%s'\n", res);
+          fail (idx);
+        }
+      xfree (res);
+    }
+}
+
+
 int
 main (int argc, char **argv)
 {
@@ -1213,6 +1311,7 @@ main (int argc, char **argv)
   test_split_fields_colon ();
   test_compare_version_strings ();
   test_format_text ();
+  test_substitute_envvars ();
 
   xfree (home_buffer);
   return !!errcount;