Simplify PDF_DecodeText() and new helper functions
I kept the code as-is when moving it. Now that it's moved and untangled,
we can simplify the code a bit.
Every modified function is supposed to have exactly the same behavior
as it had before this change. They no longer write to a `uint16_t`
temporary, so they no longer truncate characters to 16-bits, but
the caller only passed in 16-bit data in both cases, so no effective
behavior change.
(A future change will call StripLanguageCodes() with the output of
an UTF-8 decoder, which can pass 32-bit characters. For that future
use-case, the change is a progression.)
Bug: pdfium:2101
Change-Id: If56afbadb8282b042f4411a5d1930543c67a197b
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/113810
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
diff --git a/core/fpdfapi/parser/fpdf_parser_decode.cpp b/core/fpdfapi/parser/fpdf_parser_decode.cpp
index 78b81c1..47b5e43 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode.cpp
@@ -32,14 +32,6 @@
const uint32_t kMaxStreamSize = 20 * 1024 * 1024;
-uint16_t GetUnicodeFromBigEndianBytes(const uint8_t* bytes) {
- return bytes[0] << 8 | bytes[1];
-}
-
-uint16_t GetUnicodeFromLittleEndianBytes(const uint8_t* bytes) {
- return bytes[1] << 8 | bytes[0];
-}
-
bool CheckFlateDecodeParams(int Colors, int BitsPerComponent, int Columns) {
if (Colors < 0 || BitsPerComponent < 0 || Columns < 0)
return false;
@@ -477,29 +469,15 @@
#if defined(WCHAR_T_IS_32_BIT)
static size_t FuseSurrogates(pdfium::span<wchar_t> s, size_t n) {
size_t dest_pos = 0;
- char16_t high_surrogate = 0;
for (size_t i = 0; i < n; ++i) {
- uint16_t unicode = s[i];
-
// TODO(crbug.com/pdfium/2031): Always use UTF-16.
- if (high_surrogate) {
- char16_t previous_high_surrogate = high_surrogate;
- high_surrogate = 0;
- if (pdfium::IsLowSurrogate(unicode)) {
- s[dest_pos++] = pdfium::SurrogatePair(previous_high_surrogate, unicode)
- .ToCodePoint();
- continue;
- }
- s[dest_pos++] = previous_high_surrogate;
- }
- if (pdfium::IsHighSurrogate(unicode)) {
- high_surrogate = unicode;
+ if (pdfium::IsHighSurrogate(s[i]) && i + 1 < n &&
+ pdfium::IsLowSurrogate(s[i + 1])) {
+ s[dest_pos++] = pdfium::SurrogatePair(s[i], s[i + 1]).ToCodePoint();
+ ++i;
continue;
}
- s[dest_pos++] = unicode;
- }
- if (high_surrogate) {
- s[dest_pos++] = high_surrogate;
+ s[dest_pos++] = s[i];
}
return dest_pos;
}
@@ -508,28 +486,15 @@
static size_t StripLanguageCodes(pdfium::span<wchar_t> s, size_t n) {
size_t dest_pos = 0;
for (size_t i = 0; i < n; ++i) {
- uint16_t unicode = s[i];
-
// 0x001B is a begin/end marker for language metadata region that
// should not be in the decoded text.
- if (unicode == 0x001B) {
- ++i;
- for (; i < n; ++i) {
- unicode = s[i];
- if (unicode == 0x001B) {
- ++i;
- if (i < n) {
- unicode = s[i];
- }
- break;
- }
+ if (s[i] == 0x001B) {
+ for (++i; i < n && s[i] != 0x001B; ++i) {
+ // No for-loop body. The loop searches for the terminating 0x001B.
}
- if (i >= n) {
- break;
- }
+ continue;
}
-
- s[dest_pos++] = unicode;
+ s[dest_pos++] = s[i];
}
return dest_pos;
}
@@ -539,18 +504,15 @@
WideString result;
if (span.size() >= 2 && ((span[0] == 0xfe && span[1] == 0xff) ||
(span[0] == 0xff && span[1] == 0xfe))) {
- size_t max_chars = (span.size() - 2) / 2;
- if (!max_chars)
- return result;
-
- pdfium::span<wchar_t> dest_buf = result.GetBuffer(max_chars);
- uint16_t (*GetUnicodeFromBytes)(const uint8_t*) =
- span[0] == 0xfe ? GetUnicodeFromBigEndianBytes
- : GetUnicodeFromLittleEndianBytes;
- const uint8_t* unicode_str = &span[2];
-
- for (size_t i = 0; i < max_chars * 2; i += 2) {
- dest_buf[dest_pos++] = GetUnicodeFromBytes(unicode_str + i);
+ pdfium::span<wchar_t> dest_buf = result.GetBuffer((span.size() - 2) / 2);
+ if (span[0] == 0xfe) {
+ for (size_t i = 2; i < span.size() - 1; i += 2) {
+ dest_buf[dest_pos++] = span[i] << 8 | span[i + 1];
+ }
+ } else {
+ for (size_t i = 2; i < span.size() - 1; i += 2) {
+ dest_buf[dest_pos++] = span[i + 1] << 8 | span[i];
+ }
}
dest_pos = StripLanguageCodes(dest_buf, dest_pos);
