[GitHub] [arrow] augustoasilva commented on a change in pull request #11551: ARROW-14482: [C++][Gandiva] Implement MASK_FIRST_N and MASK_LAST_N functions

[GitBox <gi...@apache.org>]

augustoasilva commented on a change in pull request #11551:
URL: https://github.com/apache/arrow/pull/11551#discussion_r760056622



##########
File path: cpp/src/gandiva/gdv_function_stubs.cc
##########
@@ -832,6 +850,201 @@ const char* gdv_fn_initcap_utf8(int64_t context, const char* data, int32_t data_
   *out_len = out_idx;
   return out;
 }
+
+GANDIVA_EXPORT
+const char* gdv_mask_first_n_utf8_int32(int64_t context, const char* data,
+                                        int32_t data_len, int32_t n_to_mask,
+                                        int32_t* out_len) {
+  if (data_len <= 0) {
+    *out_len = 0;
+    return nullptr;
+  }
+
+  if (n_to_mask > data_len) {
+    n_to_mask = data_len;
+  }
+
+  *out_len = data_len;
+
+  if (n_to_mask <= 0) {
+    return data;
+  }
+
+  char* out = reinterpret_cast<char*>(gdv_fn_context_arena_malloc(context, *out_len));
+  if (out == nullptr) {
+    gdv_fn_context_set_error_msg(context, "Could not allocate memory for output string");
+    *out_len = 0;
+    return nullptr;
+  }
+
+  int bytes_masked;
+  for (bytes_masked = 0; bytes_masked < n_to_mask; bytes_masked++) {
+    unsigned char char_single_byte = data[bytes_masked];
+    if (char_single_byte > 127) {
+      // found a multi-byte utf-8 char
+      break;
+    }
+    out[bytes_masked] = mask_array[char_single_byte];
+  }
+
+  int chars_masked = bytes_masked;
+  int out_idx = bytes_masked;
+
+  // Handle multibyte utf8 characters
+  utf8proc_int32_t utf8_char;
+  while ((chars_masked < n_to_mask) && (bytes_masked < data_len)) {
+    auto char_len =
+        utf8proc_iterate(reinterpret_cast<const utf8proc_uint8_t*>(data + bytes_masked),
+                         data_len, &utf8_char);
+
+    if (char_len < 0) {
+      gdv_fn_context_set_error_msg(context, utf8proc_errmsg(char_len));
+      *out_len = 0;
+      return nullptr;
+    }
+
+    switch (utf8proc_category(utf8_char)) {
+      case 1:
+        out[out_idx] = 'X';
+        out_idx++;
+        break;
+      case 2:
+        out[out_idx] = 'x';
+        out_idx++;
+        break;
+      case 9:
+        out[out_idx] = 'n';
+        out_idx++;
+        break;
+      case 10:
+        out[out_idx] = 'n';
+        out_idx++;
+        break;
+      default:
+        memcpy(out + out_idx, data + bytes_masked, char_len);
+        out_idx += static_cast<int>(char_len);
+        break;
+    }
+    bytes_masked += static_cast<int>(char_len);
+    chars_masked++;
+  }
+
+  // Correct the out_len after masking multibyte characters with single byte characters
+  *out_len = *out_len - (bytes_masked - out_idx);
+
+  if (bytes_masked < data_len) {
+    memcpy(out + out_idx, data + bytes_masked, data_len - bytes_masked);
+  }
+
+  return out;
+}
+
+GANDIVA_EXPORT
+const char* gdv_mask_last_n_utf8_int32(int64_t context, const char* data,
+                                       int32_t data_len, int32_t n_to_mask,
+                                       int32_t* out_len) {
+  if (data_len <= 0) {
+    *out_len = 0;
+    return nullptr;
+  }
+
+  if (n_to_mask > data_len) {
+    n_to_mask = data_len;
+  }
+
+  *out_len = data_len;
+
+  if (n_to_mask <= 0) {
+    return data;
+  }
+
+  char* out = reinterpret_cast<char*>(gdv_fn_context_arena_malloc(context, *out_len));
+  if (out == nullptr) {
+    gdv_fn_context_set_error_msg(context, "Could not allocate memory for output string");
+    *out_len = 0;
+    return nullptr;
+  }
+
+  bool has_multi_byte = false;
+  for (int i = 0; i < data_len; i++) {
+    unsigned char char_single_byte = data[i];
+    if (char_single_byte > 127) {
+      // found a multi-byte utf-8 char
+      has_multi_byte = true;
+      break;
+    }
+  }
+
+  if (!has_multi_byte) {
+    int start_idx = data_len - n_to_mask;
+    for (int i = start_idx; i < data_len; ++i) {
+      unsigned char char_single_byte = data[i];
+      out[i] = mask_array[char_single_byte];
+    }
+    memcpy(out, data, start_idx);

Review comment:
       Sure, moved it.




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