3 files changed, 128 insertions, 3 deletions

diff --git a/usr/src/lib/libcustr/common/custr.c b/usr/src/lib/libcustr/common/custr.c
index 8c8288ab7d..3ff67cac71 100644
--- a/usr/src/lib/libcustr/common/custr.c
+++ b/usr/src/lib/libcustr/common/custr.c
@@ -14,7 +14,7 @@
  */
 
 /*
- * Copyright 2019 Joyent, Inc.
+ * Copyright 2020 Joyent, Inc.
  */
 
 #include <stdlib.h>
@@ -85,6 +85,81 @@ custr_reset(custr_t *cus)
 	cus->cus_data[0] = '\0';
 }
 
+int
+custr_remove(custr_t *cus, size_t idx, size_t len)
+{
+	size_t endidx = idx + len;
+
+	/*
+	 * Once gcc4 is dropped as a shadow compiler, we can migrate to
+	 * using builtins for the overflow check.
+	 */
+	if (endidx < idx || endidx < len) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	if (idx >= cus->cus_strlen || endidx > cus->cus_strlen) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	if (len == 0)
+		return (0);
+
+	/* The +1 will include the terminating NUL in the move */
+	(void) memmove(cus->cus_data + idx, cus->cus_data + endidx,
+	    cus->cus_strlen - endidx + 1);
+	cus->cus_strlen -= len;
+
+	/* The result should be NUL */
+	VERIFY0(cus->cus_data[cus->cus_strlen]);
+	return (0);
+}
+
+int
+custr_rremove(custr_t *cus, size_t ridx, size_t len)
+{
+	size_t idx;
+
+	if (ridx >= cus->cus_strlen) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	idx = cus->cus_strlen - ridx - 1;
+	return (custr_remove(cus, idx, len));
+}
+
+int
+custr_trunc(custr_t *cus, size_t idx)
+{
+	if (idx >= cus->cus_strlen) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	cus->cus_data[idx] = '\0';
+	cus->cus_strlen = idx;
+	return (0);
+}
+
+int
+custr_rtrunc(custr_t *cus, size_t ridx)
+{
+	size_t idx;
+
+	if (ridx >= cus->cus_strlen) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	idx = cus->cus_strlen - ridx - 1;
+	cus->cus_data[idx] = '\0';
+	cus->cus_strlen = idx;
+	return (0);
+}
+
 size_t
 custr_len(custr_t *cus)
 {
diff --git a/usr/src/lib/libcustr/common/libcustr.h b/usr/src/lib/libcustr/common/libcustr.h
index 8fe5fee1b7..f8f15db07b 100644
--- a/usr/src/lib/libcustr/common/libcustr.h
+++ b/usr/src/lib/libcustr/common/libcustr.h
@@ -10,7 +10,7 @@
  */
 
 /*
- * Copyright 2019, Joyent, Inc.
+ * Copyright 2019 Joyent, Inc.
  */
 
 #ifndef _LIBCUSTR_H
@@ -142,6 +142,52 @@ size_t custr_len(custr_t *);
 void custr_reset(custr_t *);
 
 /*
+ * custr_remove(cus, idx, len)
+ *
+ * Remove len bytes from cus, starting at idx.
+ *
+ * Returns 0 on success or -1 on failure.  On failure, errno will be set to:
+ *	EINVAL	Either the idx or len parameter is invalid
+ *
+ */
+int custr_remove(custr_t *, size_t, size_t);
+
+/*
+ * custr_rremove(cus, idx, len)
+ *
+ * Remove len bytes from cus, starting at idx relative to the end of cus.
+ * That is, 0 = last byte of cus, 1 = second to last byte of cus, ...).
+ * The direction of removal is always towards the end of the string.  I.e.
+ * 'custr_rremove(cus, 1, 2)' removes the last two bytes of cus.
+ *
+ * Returns 0 on success or -1 on failure.  On failure, errno will be set to:
+ *	EINVAL	Either the idx or len parameter is invalid
+ *
+ */
+int custr_rremove(custr_t *, size_t, size_t);
+
+/*
+ * custr_trunc(cus, idx)
+ *
+ * Truncate cus starting at idx.
+ *
+ * Returns 0 on success or -1 on failure.  On failure, errno is set to:
+ *	EINVAL	The idx value was invalid.
+ */
+int custr_trunc(custr_t *, size_t);
+
+/*
+ * custr_rtrunc(cus, idx)
+ *
+ * Truncate cus starting at idx relative to the end of cus (similar to how
+ * the idx paramter is treated with custr_rremove()).
+ *
+ * Returns 0 on success or -1 on failure.  On failure, errno is set to:
+ *	EINVAL	The idx value was invalid.
+ */
+int custr_rtrunc(custr_t *, size_t);
+
+/*
  * Retrieve a const pointer to a NUL-terminated string version of the contents
  * of the dynamic string.  Storage for this string should not be freed, and
  * the pointer will be invalidated by any mutations to the dynamic string.
diff --git a/usr/src/lib/libcustr/common/mapfile-vers b/usr/src/lib/libcustr/common/mapfile-vers
index f94636b6f5..53b94164ad 100644
--- a/usr/src/lib/libcustr/common/mapfile-vers
+++ b/usr/src/lib/libcustr/common/mapfile-vers
@@ -10,7 +10,7 @@
 #
 
 #
-# Copyright 2019, Joyent, Inc.
+# Copyright 2019 Joyent, Inc.
 #
 
 #
@@ -42,7 +42,11 @@ SYMBOL_VERSION ILLUMOSprivate {
 	custr_cstr;
 	custr_free;
 	custr_len;
+	custr_remove;
 	custr_reset;
+	custr_rremove;
+	custr_rtrunc;
+	custr_trunc;
 	custr_xalloc;
 	custr_xalloc_buf;
     local: