1 files changed, 119 insertions, 0 deletions
diff --git a/libslang/demo/useropen.c b/libslang/demo/useropen.c
new file mode 100644
index 0000000..efb2f57
--- /dev/null
+++ b/libslang/demo/useropen.c
@@ -0,0 +1,119 @@
+/* This demo indicates how to read and parse a S-Lang file by bypassing the 
+ * built-in routines.
+ */
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#include <slang.h>
+
+/* Suppose that you want to read input using a read line package 
+ * such as one provided by S-Lang.  For generality, lets assume that this
+ * function is called 'readline' and it is prototyped as:
+ *   int readline (char *prompt, char *buffer);
+ * where it returns the number of characters read and -1 if end of file.  The
+ * first parameter is a prompt and the second represents the buffer where the
+ * characters are to placed.  Also assume that this routine requires that the 
+ * function 'init_readline' be called first before it can be used and 
+ * 'reset_readline' must be called after using it.
+ * 
+ * The goal here is to get S-Lang to call the readline function.
+ */
+
+/* For the purposes of this demo, we will use just fgets */
+#define MAX_BUF_LEN	256
+static int readline (char *prompt, char *buf)
+{
+   fputs (prompt, stdout);  fflush (stdout);
+   if (NULL == fgets (buf, MAX_BUF_LEN, stdin)) return -1;
+   return (int) strlen (buf);
+}
+
+static int init_readline (void)
+{
+   puts ("Initializing readline."); fflush (stdout);
+   return 0;
+}
+
+static void reset_readline (void)
+{
+   puts ("Resetting readline."); fflush (stdout);
+}
+ 
+/* Now lets define the function that S-Lang will use to actually read the data.
+ * It calls readline.  S-Lang will call this function and the function must 
+ * return a pointer to the buffer containg the characters of the line or NULL
+ * upon end of file.  In many ways, it is like fgets except that it is passed
+ * a pointer to SLang_Load_Type in stead of FILE.
+ */
+
+typedef struct
+{
+   char buf[MAX_BUF_LEN];
+   char *prompt;
+}
+Our_Client_Data_Type;
+
+static char *read_using_readline (SLang_Load_Type *x)
+{
+   Our_Client_Data_Type *client_data;
+
+   client_data = (Our_Client_Data_Type *) x->client_data;
+   if (-1 == readline (client_data->prompt, client_data->buf))
+     return NULL;
+   
+   return client_data->buf;
+}
+
+/* Now, we all of this is tied together in this routine which will be called
+ * from main below.
+ */
+
+static int read_input (void)
+{
+   SLang_Load_Type *x;
+   Our_Client_Data_Type client_data;
+
+   if (NULL == (x = SLallocate_load_type ("<readline>")))
+     return -1;
+   
+   client_data.prompt = "Demo> ";
+
+   x->client_data = (VOID_STAR) &client_data;
+   x->read = read_using_readline; /* function to call to perform the read */
+   SLang_load_object (x);
+   return 0;
+}
+
+/* Now here is are some intrinsic functions */
+
+int main (int argc, char **argv)
+{
+   /* usual stuff */
+   
+   (void) argc; (void) argv;
+   
+   if ((-1 == SLang_init_slang ())    /* basic interpreter functions */
+       || (-1 == SLang_init_slmath ()) 	       /* sin, cos, etc... */
+#ifdef unix
+       || (-1 == SLang_init_slunix ())	       /* unix system calls */
+#endif
+       || (-1 == SLang_init_slfile ()))	       /* file i/o */
+     {
+	fprintf(stderr, "Unable to initialize S-Lang.\n");
+	return 1;
+     }
+
+   init_readline ();
+
+   read_input ();
+   
+   reset_readline ();
+   return SLang_Error;
+}
+
+
+
+