Re-implement space-related mapping functions in Sail rather than backends

Uses new primop 'string_take' which is much easier to implement in e.g. C

2 files changed, 19 insertions, 0 deletions

diff --git a/lib/sail.c b/lib/sail.c
index 9b7a1696..94cd5c2c 100644
--- a/lib/sail.c
+++ b/lib/sail.c
@@ -151,7 +151,25 @@ void string_drop(sail_string *dst, sail_string s, sail_int ns)
     *dst = realloc(*dst, (len - n) + 1);
     memcpy(*dst, s + n, len - n);
     (*dst)[len - n] = '\0';
+  } else {
+    *dst = realloc(*dst, 1);
+    **dst = '\0';
+  }
+}
+
+void string_take(sail_string *dst, sail_string s, sail_int ns)
+{
+  size_t len = strlen(s);
+  mach_int n = CREATE_OF(mach_int, sail_int)(ns);
+  mach_int to_copy;
+  if (len <= n) {
+    to_copy = len;
+  } else {
+    to_copy = n;
   }
+  *dst = realloc(*dst, to_copy + 1);
+  memcpy(*dst, s, to_copy);
+  *dst[to_copy] = '\0';
 }
 
 /* ***** Sail integers ***** */
diff --git a/lib/sail.h b/lib/sail.h
index 598ac67d..4ccd8b93 100644
--- a/lib/sail.h
+++ b/lib/sail.h
@@ -327,6 +327,7 @@ void random_real(real *rop, unit);
 
 void string_length(sail_int *len, sail_string s);
 void string_drop(sail_string *dst, sail_string s, sail_int len);
+void string_take(sail_string *dst, sail_string s, sail_int len);
 
 /* ***** Printing ***** */