ffi: variable length zarray needs in operation.

* ffi.c (ffi_varray_null_term_in): New static function.
(ffi_type_compile): Wire in new function as in operation
of variable length zarray.

* txr.1: Documented.

2 files changed, 47 insertions, 1 deletions

diff --git a/ffi.c b/ffi.c
index 5624b9dd..31666020 100644
--- a/ffi.c
+++ b/ffi.c
@@ -1345,6 +1345,39 @@ static val ffi_varray_in(struct txr_ffi_type *tft, int copy, mem_t *src,
   return ffi_array_in_common(tft, copy, src, vec, self, nelem);
 }
 
+static val ffi_varray_null_term_in(struct txr_ffi_type *tft, int copy, mem_t *src,
+                                   val vec_in, val self)
+{
+  val vec = vector(zero, nil);
+  val eltype = tft->mtypes;
+  struct txr_ffi_type *etft = ffi_type_struct(eltype);
+  cnum elsize = etft->size;
+  cnum offs, i;
+
+  for (i = 0, offs = 0; ; i++) {
+    mem_t *el = src + offs, *p;
+
+    for (p = el; p < el + elsize; p++)
+      if (*p)
+        break;
+
+    if (p == el + elsize)
+      break;
+
+    if (etft->in != 0) {
+      val elval = ref(vec, num_fast(i));
+      vec_push(vec, elval);
+    } else if (copy) {
+      val elval = etft->get(etft, src + offs, self);
+      vec_push(vec, elval);
+    }
+
+    offs += elsize;
+  }
+
+  return replace(vec_in, vec, 0, length_vec(vec));
+}
+
 static val ffi_varray_null_term_get(struct txr_ffi_type *tft, mem_t *src,
                                     val self)
 {
@@ -1623,6 +1656,7 @@ val ffi_type_compile(val syntax)
         if (sym == zarray_s) {
           tft->null_term = 1;
           tft->get = ffi_varray_null_term_get;
+          tft->in = ffi_varray_null_term_in;
         }
         tft->alloc = ffi_varray_alloc;
         tft->free = free;
diff --git a/txr.1 b/txr.1
index df361b52..c5fcee5c 100644
--- a/txr.1
+++ b/txr.1
@@ -53719,7 +53719,19 @@ the
 .code zarray
 type supports the get operation, which extracts elements, accumulating them
 into a resulting vector, until it encounters an element consisting of all zero
-bytes.
+bytes. That element terminates the decoding, and isn't included in the
+resulting array.
+
+The variable-length
+.code zarray
+also has a special in operation. Like the get operation, the in operation
+extracts all elements until a terminating null, decoding them to a vector.
+Then, a range of the original vector object is replaced with the decoded vector.
+If the decoded vector is as long, or longer, than the original, all of the
+elements of the original are replaced and its length is extended as necessary
+to contain all of the new elements. If the decoded vector is shorter than the
+decoded one, then it replaces a range of the original one corresponding to
+its length.
 
 .meIP (ptr << type )
 The