diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 89a84071..f99f1771 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -1,6 +1,8 @@
 add_library(libprjxray
-	memory_mapped_file.cc)
+	memory_mapped_file.cc
+	segbits_file_reader.cc)
 target_include_directories(libprjxray PUBLIC "include")
+target_link_libraries(libprjxray absl::strings)
 
 if (PRJXRAY_BUILD_TESTING)
 	add_executable(memory_mapped_file_test memory_mapped_file_test.cc)
@@ -8,4 +10,10 @@ if (PRJXRAY_BUILD_TESTING)
 	add_test(NAME memory_mapped_file_test
 		 COMMAND memory_mapped_file_test
 		 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/test_data)
+
+	add_executable(segbits_file_reader_test segbits_file_reader_test.cc)
+	target_link_libraries(segbits_file_reader_test libprjxray gtest_main)
+	add_test(NAME segbits_file_reader_test
+		 COMMAND segbits_file_reader_test
+		 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/test_data)
 endif()
diff --git a/lib/include/prjxray/segbits_file_reader.h b/lib/include/prjxray/segbits_file_reader.h
new file mode 100644
index 00000000..277eba1c
--- /dev/null
+++ b/lib/include/prjxray/segbits_file_reader.h
@@ -0,0 +1,67 @@
+#ifndef PRJXRAY_LIB_SEGBITS_FILE_READER_H
+#define PRJXRAY_LIB_SEGBITS_FILE_READER_H
+
+#include <iterator>
+#include <memory>
+
+#include <absl/strings/string_view.h>
+#include <prjxray/memory_mapped_file.h>
+
+namespace prjxray {
+
+class SegbitsFileReader {
+ public:
+	class value_type {
+	 public:
+		absl::string_view tag() const { return tag_; }
+		absl::string_view bit() const { return bit_; }
+
+	 private:
+		friend SegbitsFileReader;
+
+		value_type(const absl::string_view &view);
+
+		absl::string_view tag_;
+		absl::string_view bit_;
+	};
+
+	class iterator
+		: public std::iterator<std::input_iterator_tag, value_type> {
+	 public:
+		iterator& operator++();
+
+		bool operator==(iterator other) const {
+			return view_ == other.view_; }
+		bool operator!=(iterator other) const {
+			return !(*this == other);}
+
+		const value_type& operator*() const { return value_; }
+		const value_type* operator->() const { return &value_; }
+
+	 protected:
+		explicit iterator(absl::string_view view)
+			: view_(view), value_(view) {}
+
+	 private:
+		friend SegbitsFileReader;
+
+		absl::string_view view_;
+		value_type value_;
+	};
+
+	static std::unique_ptr<SegbitsFileReader> InitWithFile(
+		const std::string &path);
+
+	iterator begin();
+	iterator end();
+
+ private:
+	SegbitsFileReader(std::unique_ptr<MemoryMappedFile> &&mapped_file)
+		: mapped_file_(std::move(mapped_file)) {};
+
+	std::unique_ptr<MemoryMappedFile> mapped_file_;
+};
+
+} // namespace prjxray
+
+#endif  // PRJXRAY_LIB_SEGBITS_FILE_READER_H
diff --git a/lib/segbits_file_reader.cc b/lib/segbits_file_reader.cc
new file mode 100644
index 00000000..96e06ed9
--- /dev/null
+++ b/lib/segbits_file_reader.cc
@@ -0,0 +1,59 @@
+#include <prjxray/segbits_file_reader.h>
+
+namespace prjxray {
+
+std::unique_ptr<SegbitsFileReader> SegbitsFileReader::InitWithFile(
+	const std::string &path) {
+
+	auto mapped_file = MemoryMappedFile::InitWithFile(path);
+	if (!mapped_file) return nullptr;
+
+	return std::unique_ptr<SegbitsFileReader>(
+		new SegbitsFileReader(std::move(mapped_file)));
+}
+
+SegbitsFileReader::iterator SegbitsFileReader::begin() {
+	return iterator(absl::string_view(
+			static_cast<const char*>(mapped_file_->data()),
+			mapped_file_->size()));
+}
+
+SegbitsFileReader::iterator SegbitsFileReader::end() {
+	return iterator(absl::string_view());
+}
+
+SegbitsFileReader::value_type::value_type(const absl::string_view &view) {
+	size_t separator_start = view.find_first_of(" \t");
+	if (separator_start == absl::string_view::npos) {
+		tag_ = view;
+		bit_ = absl::string_view();
+		return;
+	}
+
+	size_t bit_start = view.find_first_not_of(" \t", separator_start);
+	size_t newline = view.find('\n', bit_start);
+	if (newline == absl::string_view::npos) {
+		tag_ = view.substr(0, separator_start);
+		bit_ = view.substr(bit_start);
+		return;
+	}
+
+	size_t bit_len = newline - bit_start;
+	tag_ = view.substr(0, separator_start);
+	bit_ = view.substr(bit_start, bit_len);
+	return;
+}
+
+SegbitsFileReader::iterator& SegbitsFileReader::iterator::operator++() {
+	size_t newline = view_.find('\n');
+	if (newline == absl::string_view::npos) {
+		view_ = absl::string_view();
+	}
+
+	view_.remove_prefix(newline + 1);
+	value_ = value_type(view_);
+	return *this;
+}
+
+
+}  // namespace prjxray
diff --git a/lib/segbits_file_reader_test.cc b/lib/segbits_file_reader_test.cc
new file mode 100644
index 00000000..35764f24
--- /dev/null
+++ b/lib/segbits_file_reader_test.cc
@@ -0,0 +1,82 @@
+#include <prjxray/segbits_file_reader.h>
+
+#include <map>
+#include <string>
+
+#include <gtest/gtest.h>
+
+TEST(SegbitsFileReaderTest, NonExistantFileReturnsNull) {
+	EXPECT_FALSE(prjxray::SegbitsFileReader::InitWithFile("does_not_exist"));
+}
+
+TEST(SegbitsFileReaderTest, ZeroLengthFileYieldsNoItems) {
+	auto segbits_reader =
+		prjxray::SegbitsFileReader::InitWithFile("empty_file");
+	ASSERT_TRUE(segbits_reader);
+
+	EXPECT_EQ(segbits_reader->begin(), segbits_reader->end());
+}
+
+TEST(SegbitsFileReaderTest, FileWithOneEntry) {
+	auto segbits_reader =
+		prjxray::SegbitsFileReader::InitWithFile("one_entry.segbits");
+	ASSERT_TRUE(segbits_reader);
+
+	auto begin_iter = segbits_reader->begin();
+	EXPECT_EQ(begin_iter->tag(), "CLBLL_L.SLICEL_X0.A5FF.ZINI");
+	EXPECT_EQ(begin_iter->bit(), "31_06");
+
+	EXPECT_EQ(++begin_iter, segbits_reader->end());
+}
+
+TEST(SegbitsFileReaderTest, FileWithOneEntryWithEmptyTag) {
+	auto segbits_reader = prjxray::SegbitsFileReader::InitWithFile(
+		"one_entry_empty_tag.segbits");
+	ASSERT_TRUE(segbits_reader);
+
+	auto begin_iter = segbits_reader->begin();
+	EXPECT_EQ(begin_iter->tag(), "");
+	EXPECT_EQ(begin_iter->bit(), "31_06");
+
+	EXPECT_EQ(++begin_iter, segbits_reader->end());
+}
+
+TEST(SegbitsFileReaderTest, FileWithOneEntryMissingBit) {
+	auto segbits_reader = prjxray::SegbitsFileReader::InitWithFile(
+		"one_entry_missing_bit.segbits");
+	ASSERT_TRUE(segbits_reader);
+
+	auto begin_iter = segbits_reader->begin();
+	EXPECT_EQ(begin_iter->tag(), "CLBLL_L.SLICEL_X0.A5FF.ZINI");
+	EXPECT_EQ(begin_iter->bit(), "");
+
+	EXPECT_EQ(++begin_iter, segbits_reader->end());
+}
+
+TEST(SegbitsFileReaderTest, FileWithOneEntryWithExtraWhitespace) {
+	auto segbits_reader = prjxray::SegbitsFileReader::InitWithFile(
+		"one_entry_extra_whitespace.segbits");
+	ASSERT_TRUE(segbits_reader);
+
+	auto begin_iter = segbits_reader->begin();
+	EXPECT_EQ(begin_iter->tag(), "CLBLL_L.SLICEL_X0.A5FF.ZINI");
+	EXPECT_EQ(begin_iter->bit(), "31_06");
+
+	EXPECT_EQ(++begin_iter, segbits_reader->end());
+}
+
+TEST(SegbitsFileReaderTest, FileWithTwoEntries) {
+	auto segbits_reader = prjxray::SegbitsFileReader::InitWithFile(
+		"two_entries.segbits");
+	ASSERT_TRUE(segbits_reader);
+
+	auto iter = segbits_reader->begin();
+	EXPECT_EQ(iter->tag(), "CLBLL_L.SLICEL_X0.A5FF.ZINI");
+	EXPECT_EQ(iter->bit(), "31_06");
+
+	++iter;
+	EXPECT_EQ(iter->tag(), "CLBLL_L.SLICEL_X0.AFF.ZINI");
+	EXPECT_EQ(iter->bit(), "31_03");
+
+	EXPECT_EQ(++iter, segbits_reader->end());
+}
diff --git a/lib/test_data/one_entry.segbits b/lib/test_data/one_entry.segbits
new file mode 100644
index 00000000..eee8c450
--- /dev/null
+++ b/lib/test_data/one_entry.segbits
@@ -0,0 +1 @@
+CLBLL_L.SLICEL_X0.A5FF.ZINI 31_06
diff --git a/lib/test_data/one_entry_empty_tag.segbits b/lib/test_data/one_entry_empty_tag.segbits
new file mode 100644
index 00000000..cc99b3fe
--- /dev/null
+++ b/lib/test_data/one_entry_empty_tag.segbits
@@ -0,0 +1 @@
+ 31_06
diff --git a/lib/test_data/one_entry_extra_whitespace.segbits b/lib/test_data/one_entry_extra_whitespace.segbits
new file mode 100644
index 00000000..12d1135b
--- /dev/null
+++ b/lib/test_data/one_entry_extra_whitespace.segbits
@@ -0,0 +1 @@
+CLBLL_L.SLICEL_X0.A5FF.ZINI 	 31_06
diff --git a/lib/test_data/one_entry_missing_bit.segbits b/lib/test_data/one_entry_missing_bit.segbits
new file mode 100644
index 00000000..d1d77fe2
--- /dev/null
+++ b/lib/test_data/one_entry_missing_bit.segbits
@@ -0,0 +1 @@
+CLBLL_L.SLICEL_X0.A5FF.ZINI 
diff --git a/lib/test_data/two_entries.segbits b/lib/test_data/two_entries.segbits
new file mode 100644
index 00000000..cc6ca46f
--- /dev/null
+++ b/lib/test_data/two_entries.segbits
@@ -0,0 +1,2 @@
+CLBLL_L.SLICEL_X0.A5FF.ZINI 31_06
+CLBLL_L.SLICEL_X0.AFF.ZINI 31_03