Diff

A line-oriented textual difference implementation. More...

Classes
struct	sourcemeta::core::Diff

Functions
SOURCEMETA_CORE_DIFF_EXPORT auto	sourcemeta::core::diff (const std::string_view original, const std::string_view modified, const Diff::Mode mode, const Diff::Algorithm algorithm) -> Diff
SOURCEMETA_CORE_DIFF_EXPORT auto	sourcemeta::core::stringify (const Diff &document, std::ostream &stream, const Diff::Format format, const Diff::FormatOptions &options={}) -> void

Detailed Description

A line-oriented textual difference implementation.

This functionality is included as follows:

#include <sourcemeta/core/diff.h>

---

Class Documentation

sourcemeta::core::Diff

struct sourcemeta::core::Diff

The result of comparing two inputs, holding the tokens of each alongside the operations that relate them, plus the vocabulary that describes how a comparison is performed and rendered.

The tokens are views into the inputs that were compared, which must outlive this result.

Public Types
enum class	Mode : std::uint8_t { Line }
	The granularity at which inputs are compared. More...
enum class	Algorithm : std::uint8_t { Myers }
	The strategy used to locate the common subsequences of two inputs. More...
enum class	Format : std::uint8_t { Unified }
	The textual serialisation used to render a set of differences. More...
Public Attributes
std::vector< std::string_view >	original
	The tokens of the original input.
std::vector< std::string_view >	modified
	The tokens of the modified input.
std::vector< Operation >	operations
	The transformations that turn the original input into the modified one.
bool	original_ends_with_newline {true}
	Whether the original input ended with a line terminator.
bool	modified_ends_with_newline {true}
	Whether the modified input ended with a line terminator.

Member Enumeration Documentation

Algorithm

enum class sourcemeta::core::Diff::Algorithm : std::uint8_t

strong

The strategy used to locate the common subsequences of two inputs.

Enumerator
Myers	A greedy shortest edit script search over the edit graph, as described by Eugene W. Myers in "An O(ND) Difference Algorithm and Its Variations", Algorithmica Vol. 1, 1986, pp. 251-266 (http://www.xmailserver.org/diff2.pdf)

Format

enum class sourcemeta::core::Diff::Format : std::uint8_t

strong

The textual serialisation used to render a set of differences.

Enumerator
Unified	The unified format, as standardised by POSIX in IEEE Std 1003.1-2024 (https://pubs.opengroup.org/onlinepubs/9799919799/utilities/diff.html)

Mode

enum class sourcemeta::core::Diff::Mode : std::uint8_t

strong

The granularity at which inputs are compared.

Enumerator
Line	Compare newline-delimited lines.

Function Documentation

diff()

SOURCEMETA_CORE_DIFF_EXPORT auto sourcemeta::core::diff	(	const std::string_view	original,
		const std::string_view	modified,
		const Diff::Mode	mode,
		const Diff::Algorithm	algorithm ) -> Diff

Compute the differences between two inputs. For example:

#include <sourcemeta/core/diff.h>
#include <cassert>
#include <vector>
 
const auto result{sourcemeta::core::diff(
    "foo\nbar\n", "foo\nbaz\n", sourcemeta::core::Diff::Mode::Line,
    sourcemeta::core::Diff::Algorithm::Myers)};
 
assert((result.operations ==
        std::vector<sourcemeta::core::Diff::Operation>{
            {sourcemeta::core::Diff::Operation::Type::Equal, 0, 1, 0, 1},
            {sourcemeta::core::Diff::Operation::Type::Delete, 1, 2, 1, 1},
            {sourcemeta::core::Diff::Operation::Type::Insert, 2, 2, 1,
            2}}));

The tokens of the result are views into the given inputs, which must outlive it.

stringify()

SOURCEMETA_CORE_DIFF_EXPORT auto sourcemeta::core::stringify	(	const Diff &	document,
		std::ostream &	stream,
		const Diff::Format	format,
		const Diff::FormatOptions &	options = {} ) -> void

Render a set of differences into a given C++ standard output stream. For example:

#include <sourcemeta/core/diff.h>
#include <cassert>
#include <sstream>
 
const auto result{sourcemeta::core::diff(
    "foo\nbar\n", "foo\nbaz\n", sourcemeta::core::Diff::Mode::Line,
    sourcemeta::core::Diff::Algorithm::Myers)};
 
std::ostringstream stream;
sourcemeta::core::stringify(result, stream,
                            sourcemeta::core::Diff::Format::Unified);
 
assert(stream.str() == "--- a\n"
                       "+++ b\n"
                       "@@ -1,2 +1,2 @@\n"
                       " foo\n"
                       "-bar\n"
                       "+baz\n");