Re-land "Return pdfium::span<char> from ByteString::GetBuffer().""

This reverts commit 3d523e3cf89440e2ffc6571b1c687ad5e3f0318f.
Fixes bounding errors now caught by tests.

Change-Id: I4d0f1791bdcc45a10615a62abf7a4d20e7e538f2
Reviewed-on: https://pdfium-review.googlesource.com/30799
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

1 files changed, 25 insertions, 20 deletions

diff --git a/core/fpdfapi/parser/fpdf_parser_decode.cpp b/core/fpdfapi/parser/fpdf_parser_decode.cpp
index e879615ddd..edfbaf4331 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode.cpp
@@ -470,20 +470,22 @@ ByteString PDF_EncodeText(const wchar_t* pString, int len) {
   if (len == -1)
     len = wcslen(pString);
 
-  ByteString result;
-  char* dest_buf1 = result.GetBuffer(len);
   int i;
-  for (i = 0; i < len; ++i) {
-    int code;
-    for (code = 0; code < 256; ++code) {
-      if (PDFDocEncoding[code] == pString[i])
-        break;
-    }
+  ByteString result;
+  {
+    pdfium::span<char> dest_buf = result.GetBuffer(len);
+    for (i = 0; i < len; ++i) {
+      int code;
+      for (code = 0; code < 256; ++code) {
+        if (PDFDocEncoding[code] == pString[i])
+          break;
+      }
 
-    if (code == 256)
-      break;
+      if (code == 256)
+        break;
 
-    dest_buf1[i] = code;
+      dest_buf[i] = code;
+    }
   }
   result.ReleaseBuffer(i);
   if (i == len)
@@ -494,15 +496,18 @@ ByteString PDF_EncodeText(const wchar_t* pString, int len) {
     return result;
   }
 
-  int encLen = len * 2 + 2;
-
-  uint8_t* dest_buf2 = reinterpret_cast<uint8_t*>(result.GetBuffer(encLen));
-  dest_buf2[0] = 0xfe;
-  dest_buf2[1] = 0xff;
-  dest_buf2 += 2;
-  for (int j = 0; j < len; ++j) {
-    *dest_buf2++ = pString[j] >> 8;
-    *dest_buf2++ = static_cast<uint8_t>(pString[j]);
+  size_t dest_index = 0;
+  size_t encLen = len * 2 + 2;
+  {
+    pdfium::span<char> cspan = result.GetBuffer(encLen);
+    auto dest_buf = pdfium::make_span(reinterpret_cast<uint8_t*>(cspan.data()),
+                                      cspan.size());
+    dest_buf[dest_index++] = 0xfe;
+    dest_buf[dest_index++] = 0xff;
+    for (int j = 0; j < len; ++j) {
+      dest_buf[dest_index++] = pString[j] >> 8;
+      dest_buf[dest_index++] = static_cast<uint8_t>(pString[j]);
+    }
   }
   result.ReleaseBuffer(encLen);
   return result;