[llvm] df8dda6 - Add methods to data extractor for extracting bytes and fixed length C strings.
Greg Clayton via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 24 14:17:51 PST 2020
Author: Greg Clayton
Date: 2020-02-24T14:17:43-08:00
New Revision: df8dda67ed03f7d7ba3d9475556ab01946386852
URL: https://github.com/llvm/llvm-project/commit/df8dda67ed03f7d7ba3d9475556ab01946386852
DIFF: https://github.com/llvm/llvm-project/commit/df8dda67ed03f7d7ba3d9475556ab01946386852.diff
LOG: Add methods to data extractor for extracting bytes and fixed length C strings.
Summary:
These modificaitons will be used in D74883.
Fixed length C strings can have trailing NULLs or sometimes spaces (BSD archive files), so the fixed length C string defaults to stripping trailing NULLs, but can have the arguments specify to remove one or more kinds of spaces if needed. This is used to extract fixed length C strings from ELF NOTEs in D74883.
Reviewers: labath, dblaikie, aprantl
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74991
Added:
Modified:
llvm/include/llvm/Support/DataExtractor.h
llvm/lib/Support/DataExtractor.cpp
llvm/unittests/Support/DataExtractorTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Support/DataExtractor.h b/llvm/include/llvm/Support/DataExtractor.h
index 0be478811b22..164e5e8dcdd8 100644
--- a/llvm/include/llvm/Support/DataExtractor.h
+++ b/llvm/include/llvm/Support/DataExtractor.h
@@ -141,6 +141,62 @@ class DataExtractor {
/// a default-initialized StringRef will be returned.
StringRef getCStrRef(uint64_t *offset_ptr) const;
+ /// Extract a fixed length string from \a *OffsetPtr and consume \a Length
+ /// bytes.
+ ///
+ /// Returns a StringRef for the string from the data at the offset
+ /// pointed to by \a OffsetPtr. A fixed length C string will be extracted
+ /// and the \a OffsetPtr will be advanced by \a Length bytes.
+ ///
+ /// \param[in,out] OffsetPtr
+ /// A pointer to an offset within the data that will be advanced
+ /// by the appropriate number of bytes if the value is extracted
+ /// correctly. If the offset is out of bounds or there are not
+ /// enough bytes to extract this value, the offset will be left
+ /// unmodified.
+ ///
+ /// \param[in] Length
+ /// The length of the fixed length string to extract. If there are not
+ /// enough bytes in the data to extract the full string, the offset will
+ /// be left unmodified.
+ ///
+ /// \param[in] TrimChars
+ /// A set of characters to trim from the end of the string. Fixed length
+ /// strings are commonly either NULL terminated by one or more zero
+ /// bytes. Some clients have one or more spaces at the end of the string,
+ /// but a good default is to trim the NULL characters.
+ ///
+ /// \return
+ /// A StringRef for the C string value in the data. If the offset
+ /// pointed to by \a OffsetPtr is out of bounds, or if the
+ /// offset plus the length of the C string is out of bounds,
+ /// a default-initialized StringRef will be returned.
+ StringRef getFixedLengthString(uint64_t *OffsetPtr,
+ uint64_t Length, StringRef TrimChars = {"\0", 1}) const;
+
+ /// Extract a fixed number of bytes from the specified offset.
+ ///
+ /// Returns a StringRef for the bytes from the data at the offset
+ /// pointed to by \a OffsetPtr. A fixed length C string will be extracted
+ /// and the \a OffsetPtr will be advanced by \a Length bytes.
+ ///
+ /// \param[in,out] OffsetPtr
+ /// A pointer to an offset within the data that will be advanced
+ /// by the appropriate number of bytes if the value is extracted
+ /// correctly. If the offset is out of bounds or there are not
+ /// enough bytes to extract this value, the offset will be left
+ /// unmodified.
+ ///
+ /// \param[in] Length
+ /// The number of bytes to extract. If there are not enough bytes in the
+ /// data to extract all of the bytes, the offset will be left unmodified.
+ ///
+ /// \return
+ /// A StringRef for the extracted bytes. If the offset pointed to by
+ /// \a OffsetPtr is out of bounds, or if the offset plus the length
+ /// is out of bounds, a default-initialized StringRef will be returned.
+ StringRef getBytes(uint64_t *OffsetPtr, uint64_t Length) const;
+
/// Extract an unsigned integer of size \a byte_size from \a
/// *offset_ptr.
///
diff --git a/llvm/lib/Support/DataExtractor.cpp b/llvm/lib/Support/DataExtractor.cpp
index a98297cdb35f..3d19b4d481bb 100644
--- a/llvm/lib/Support/DataExtractor.cpp
+++ b/llvm/lib/Support/DataExtractor.cpp
@@ -171,6 +171,21 @@ StringRef DataExtractor::getCStrRef(uint64_t *offset_ptr) const {
return StringRef();
}
+StringRef DataExtractor::getFixedLengthString(uint64_t *OffsetPtr,
+ uint64_t Length,
+ StringRef TrimChars) const {
+ StringRef Bytes(getBytes(OffsetPtr, Length));
+ return Bytes.trim(TrimChars);
+}
+
+StringRef DataExtractor::getBytes(uint64_t *OffsetPtr, uint64_t Length) const {
+ if (!isValidOffsetForDataOfSize(*OffsetPtr, Length))
+ return StringRef();
+ StringRef Result = Data.substr(*OffsetPtr, Length);
+ *OffsetPtr += Length;
+ return Result;
+}
+
uint64_t DataExtractor::getULEB128(uint64_t *offset_ptr,
llvm::Error *Err) const {
assert(*offset_ptr <= Data.size());
diff --git a/llvm/unittests/Support/DataExtractorTest.cpp b/llvm/unittests/Support/DataExtractorTest.cpp
index cdb8bfdcb8b7..35b25dd389bf 100644
--- a/llvm/unittests/Support/DataExtractorTest.cpp
+++ b/llvm/unittests/Support/DataExtractorTest.cpp
@@ -278,4 +278,51 @@ TEST(DataExtractorTest, size) {
DataExtractor DE2(ArrayRef<uint8_t>(Data), false, 8);
EXPECT_EQ(DE2.size(), sizeof(Data));
}
+
+TEST(DataExtractorTest, FixedLengthString) {
+ const char Data[] = "hello\x00\x00\x00world \thola\x00";
+ DataExtractor DE(StringRef(Data, sizeof(Data)-1), false, 8);
+ uint64_t Offset = 0;
+ StringRef Str;
+ // Test extracting too many bytes doesn't modify Offset and returns None.
+ Str = DE.getFixedLengthString(&Offset, sizeof(Data));
+ EXPECT_TRUE(Str.empty());
+ EXPECT_EQ(Offset, 0u);
+
+ // Test extracting a fixed width C string with trailing NULL characters.
+ Str = DE.getFixedLengthString(&Offset, 8);
+ EXPECT_EQ(Offset, 8u);
+ EXPECT_EQ(Str.size(), 5u);
+ EXPECT_EQ(Str, "hello");
+ // Test extracting a fixed width C string with trailing space and tab
+ // characters.
+ Str = DE.getFixedLengthString(&Offset, 8, " \t");
+ EXPECT_EQ(Offset, 16u);
+ EXPECT_EQ(Str.size(), 5u);
+ EXPECT_EQ(Str, "world");
+ // Now extract a normal C string.
+ Str = DE.getCStrRef(&Offset);
+ EXPECT_EQ(Str.size(), 4u);
+ EXPECT_EQ(Str, "hola");
+}
+
+
+TEST(DataExtractorTest, GetBytes) {
+ // Use data with an embedded NULL character for good measure.
+ const char Data[] = "\x01\x02\x00\x04";
+ StringRef Bytes(Data, sizeof(Data)-1);
+ DataExtractor DE(Bytes, false, 8);
+ uint64_t Offset = 0;
+ StringRef Str;
+ // Test extracting too many bytes doesn't modify Offset and returns None.
+ Str = DE.getBytes(&Offset, sizeof(Data));
+ EXPECT_TRUE(Str.empty());
+ EXPECT_EQ(Offset, 0u);
+ // Test extracting 4 bytes from the stream.
+ Str = DE.getBytes(&Offset, 4);
+ EXPECT_EQ(Offset, 4u);
+ EXPECT_EQ(Str.size(), 4u);
+ EXPECT_EQ(Str, Bytes);
+}
+
}
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