Add the bstr history APIs

Trying out an opaque handle style

src/bstr.c

@@ -5,6 +5,12 @@
 
 #include "bstr.h"
 
+typedef struct bstr_history_struct {
+    char **strs; /* strings in our history, in reverse chronological order */
+    int len; /* number of strings in the history */
+    int pos; /* current position index in the history */
+} bstr_history_t;
+
 char *
 bstr_print(char *base, const char *fmt, ...)
 {
@@ -35,3 +41,77 @@ bstr_print(char *base, const char *fmt, ...)
         return base;
     }
 }
+
+bstr_history_handle
+bstr_history_create(void)
+{
+    bstr_history_t *ret = calloc(1, sizeof(bstr_history_t));
+    ret->pos = -1;
+    return ret;
+}
+
+const char *
+bstr_history_atpos(bstr_history_handle hist)
+{
+    if ((hist->len == 0) || (hist->pos < 0)) {
+        return NULL;
+    } else {
+        return hist->strs[hist->pos];
+    }
+}
+
+void
+bstr_history_new_entry(bstr_history_handle hist, const char *str)
+{
+    /* stored in reverse chronological order */
+    hist->len++;
+    hist->strs = realloc(hist->strs, sizeof(char *) * hist->len);
+    hist->strs[hist->len-1] = strdup(str);
+}
+
+void
+bstr_history_older(bstr_history_handle hist)
+{
+    if (hist->len == 0)
+        return;
+
+    if (hist->pos == -1) {
+        hist->pos = hist->len - 1;
+    } else {
+        hist->pos--;
+    }
+
+    if (hist->pos < 0)
+        hist->pos = 0;
+}
+
+void
+bstr_history_newer(bstr_history_handle hist)
+{
+    if ((hist->len == 0) || (hist->pos == -1))
+        return;
+
+    hist->pos++;
+    if (hist->pos >= hist->len)
+        hist->pos = -1;
+}
+
+void
+bstr_history_unset_pos(bstr_history_handle hist)
+{
+    hist->pos = -1;
+}
+
+void
+bstr_history_destroy(bstr_history_handle hist)
+{
+    if (!hist)
+        return;
+
+    if (hist->len > 0) {
+        for (int i = 0; i < hist->len; i++) {
+            free(hist->strs[i]);
+        }
+        free(hist->strs);
+    }
+}

src/bstr.h

@@ -4,9 +4,37 @@
 #include <stdarg.h>
 #include <stdio.h>
 
+typedef struct bstr_history_struct * bstr_history_handle;
+
+
 /* printf onto the end of base, reallocating and returning that buffer
  * can provide NULL for no base */
 __attribute__((format(printf, 2, 3)))
 char *bstr_print(char *base, const char *fmt, ...);
 
+/* Create a new bstr_history struct. The position of the history will start as
+ * unset. */
+bstr_history_handle bstr_history_create(void);
+
+/* return the string at the current history position (NULL if empty or position
+ * is not set) */
+const char *bstr_history_atpos(bstr_history_handle hist);
+
+/* Put a new entry into the history */
+void bstr_history_new_entry(bstr_history_handle hist, const char *str);
+
+/* Move the postition index one entry older. If the history position is unset,
+ * it is set to the newest entry. */
+void bstr_history_older(bstr_history_handle hist);
+
+/* Move the position index one entry newer. If the position is at the newest
+ * entry, it becomes unset. If the position is unset, it stays unset. */
+void bstr_history_newer(bstr_history_handle hist);
+
+/* Unset the history position index */
+void bstr_history_unset_pos(bstr_history_handle hist);
+
+/* destroy/free a bstr_history */
+void bstr_history_destroy(bstr_history_handle hist);
+
 #endif /* _BSTR_H_ */