7123 - tile: truncate string if necessary

1 files changed, 86 insertions, 0 deletions

diff --git a/411string.mu b/411string.mu
new file mode 100644
index 00000000..978b2094
--- /dev/null
+++ b/411string.mu
@@ -0,0 +1,86 @@
+# read up to 'len' graphemes after skipping the first 'start' ones
+fn substring in: (addr array byte), start: int, len: int, out-ah: (addr handle array byte) {
+  var in-stream: (stream byte 0x100)
+  var in-stream-addr/esi: (addr stream byte) <- address in-stream
+  write in-stream-addr, in
+  var out-stream: (stream byte 0x100)
+  var out-stream-addr/edi: (addr stream byte) <- address out-stream
+  $substring:core: {
+    # skip 'start' graphemes
+    var i/eax: int <- copy 0
+    {
+      compare i, start
+      break-if->=
+      {
+        var dummy/eax: grapheme <- read-grapheme in-stream-addr
+        compare dummy, 0xffffffff  # end-of-file
+        break-if-= $substring:core
+      }
+      i <- increment
+      loop
+    }
+    # copy 'len' graphemes
+    i <- copy 0
+    {
+      compare i, len
+      break-if->=
+      {
+        var g/eax: grapheme <- read-grapheme in-stream-addr
+        compare g, 0xffffffff  # end-of-file
+        break-if-= $substring:core
+        write-grapheme out-stream-addr, g
+      }
+      i <- increment
+      loop
+    }
+  }
+  stream-to-array out-stream-addr, out-ah
+}
+
+fn test-substring {
+  var out-h: (handle array byte)
+  var out-ah/edi: (addr handle array byte) <- address out-h
+  # prefix substrings
+  substring 0, 0, 3, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "", "F - test-substring/null"
+  substring "", 0, 3, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+#?   print-string-to-real-screen out
+#?   print-string-to-real-screen "\n"
+  check-strings-equal out, "", "F - test-substring/empty"
+  #
+  substring "abcde", 0, 3, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+#?   print-string-to-real-screen out
+#?   print-string-to-real-screen "\n"
+  check-strings-equal out, "abc", "F - test-substring/truncate"
+  #
+  substring "abcde", 0, 5, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "abcde", "F - test-substring/all"
+  #
+  substring "abcde", 0, 7, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "abcde", "F - test-substring/too-small"
+  # substrings outside string
+  substring "abcde", 6, 1, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "", "F - test-substring/start-too-large"
+  # trim prefix
+  substring "", 2, 3, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "", "F - test-substring/middle-empty"
+  #
+  substring "abcde", 1, 2, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "bc", "F - test-substring/middle-truncate"
+  #
+  substring "abcde", 1, 4, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "bcde", "F - test-substring/middle-all"
+  #
+  substring "abcde", 1, 5, out-ah
+  var out/eax: (addr array byte) <- lookup *out-ah
+  check-strings-equal out, "bcde", "F - test-substring/middle-too-small"
+}