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Diffstat (limited to 'vendor/github.com/pmezard/go-difflib/difflib/difflib.go')
| -rw-r--r-- | vendor/github.com/pmezard/go-difflib/difflib/difflib.go | 758 |
1 files changed, 758 insertions, 0 deletions
diff --git a/vendor/github.com/pmezard/go-difflib/difflib/difflib.go b/vendor/github.com/pmezard/go-difflib/difflib/difflib.go new file mode 100644 index 0000000..64cc40f --- /dev/null +++ b/vendor/github.com/pmezard/go-difflib/difflib/difflib.go @@ -0,0 +1,758 @@ +// Package difflib is a partial port of Python difflib module. +// +// It provides tools to compare sequences of strings and generate textual diffs. +// +// The following class and functions have been ported: +// +// - SequenceMatcher +// +// - unified_diff +// +// - context_diff +// +// Getting unified diffs was the main goal of the port. Keep in mind this code +// is mostly suitable to output text differences in a human friendly way, there +// are no guarantees generated diffs are consumable by patch(1). +package difflib + +import ( + "bufio" + "bytes" + "fmt" + "io" + "strings" +) + +func min(a, b int) int { + if a < b { + return a + } + return b +} + +func max(a, b int) int { + if a > b { + return a + } + return b +} + +func calculateRatio(matches, length int) float64 { + if length > 0 { + return 2.0 * float64(matches) / float64(length) + } + return 1.0 +} + +type Match struct { + A int + B int + Size int +} + +type OpCode struct { + Tag byte + I1 int + I2 int + J1 int + J2 int +} + +// SequenceMatcher compares sequence of strings. The basic +// algorithm predates, and is a little fancier than, an algorithm +// published in the late 1980's by Ratcliff and Obershelp under the +// hyperbolic name "gestalt pattern matching". The basic idea is to find +// the longest contiguous matching subsequence that contains no "junk" +// elements (R-O doesn't address junk). The same idea is then applied +// recursively to the pieces of the sequences to the left and to the right +// of the matching subsequence. This does not yield minimal edit +// sequences, but does tend to yield matches that "look right" to people. +// +// SequenceMatcher tries to compute a "human-friendly diff" between two +// sequences. Unlike e.g. UNIX(tm) diff, the fundamental notion is the +// longest *contiguous* & junk-free matching subsequence. That's what +// catches peoples' eyes. The Windows(tm) windiff has another interesting +// notion, pairing up elements that appear uniquely in each sequence. +// That, and the method here, appear to yield more intuitive difference +// reports than does diff. This method appears to be the least vulnerable +// to synching up on blocks of "junk lines", though (like blank lines in +// ordinary text files, or maybe "<P>" lines in HTML files). That may be +// because this is the only method of the 3 that has a *concept* of +// "junk" <wink>. +// +// Timing: Basic R-O is cubic time worst case and quadratic time expected +// case. SequenceMatcher is quadratic time for the worst case and has +// expected-case behavior dependent in a complicated way on how many +// elements the sequences have in common; best case time is linear. +type SequenceMatcher struct { + a []string + b []string + b2j map[string][]int + IsJunk func(string) bool + autoJunk bool + bJunk map[string]struct{} + matchingBlocks []Match + fullBCount map[string]int + bPopular map[string]struct{} + opCodes []OpCode +} + +func NewMatcher(a, b []string) *SequenceMatcher { + m := SequenceMatcher{autoJunk: true} + m.SetSeqs(a, b) + return &m +} + +func NewMatcherWithJunk(a, b []string, autoJunk bool, + isJunk func(string) bool) *SequenceMatcher { + + m := SequenceMatcher{IsJunk: isJunk, autoJunk: autoJunk} + m.SetSeqs(a, b) + return &m +} + +// Set two sequences to be compared. +func (m *SequenceMatcher) SetSeqs(a, b []string) { + m.SetSeq1(a) + m.SetSeq2(b) +} + +// Set the first sequence to be compared. The second sequence to be compared is +// not changed. +// +// SequenceMatcher computes and caches detailed information about the second +// sequence, so if you want to compare one sequence S against many sequences, +// use .SetSeq2(s) once and call .SetSeq1(x) repeatedly for each of the other +// sequences. +// +// See also SetSeqs() and SetSeq2(). +func (m *SequenceMatcher) SetSeq1(a []string) { + if &a == &m.a { + return + } + m.a = a + m.matchingBlocks = nil + m.opCodes = nil +} + +// Set the second sequence to be compared. The first sequence to be compared is +// not changed. +func (m *SequenceMatcher) SetSeq2(b []string) { + if &b == &m.b { + return + } + m.b = b + m.matchingBlocks = nil + m.opCodes = nil + m.fullBCount = nil + m.chainB() +} + +func (m *SequenceMatcher) chainB() { + // Populate line -> index mapping + b2j := map[string][]int{} + for i, s := range m.b { + indices := b2j[s] + indices = append(indices, i) + b2j[s] = indices + } + + // Purge junk elements + m.bJunk = map[string]struct{}{} + if m.IsJunk != nil { + junk := m.bJunk + for s, _ := range b2j { + if m.IsJunk(s) { + junk[s] = struct{}{} + } + } + for s, _ := range junk { + delete(b2j, s) + } + } + + // Purge remaining popular elements + popular := map[string]struct{}{} + n := len(m.b) + if m.autoJunk && n >= 200 { + ntest := n/100 + 1 + for s, indices := range b2j { + if len(indices) > ntest { + popular[s] = struct{}{} + } + } + for s, _ := range popular { + delete(b2j, s) + } + } + m.bPopular = popular + m.b2j = b2j +} + +func (m *SequenceMatcher) isBJunk(s string) bool { + _, ok := m.bJunk[s] + return ok +} + +// Find longest matching block in a[alo:ahi] and b[blo:bhi]. +// +// If IsJunk is not defined: +// +// Return (i,j,k) such that a[i:i+k] is equal to b[j:j+k], where +// alo <= i <= i+k <= ahi +// blo <= j <= j+k <= bhi +// and for all (i',j',k') meeting those conditions, +// k >= k' +// i <= i' +// and if i == i', j <= j' +// +// In other words, of all maximal matching blocks, return one that +// starts earliest in a, and of all those maximal matching blocks that +// start earliest in a, return the one that starts earliest in b. +// +// If IsJunk is defined, first the longest matching block is +// determined as above, but with the additional restriction that no +// junk element appears in the block. Then that block is extended as +// far as possible by matching (only) junk elements on both sides. So +// the resulting block never matches on junk except as identical junk +// happens to be adjacent to an "interesting" match. +// +// If no blocks match, return (alo, blo, 0). +func (m *SequenceMatcher) findLongestMatch(alo, ahi, blo, bhi int) Match { + // CAUTION: stripping common prefix or suffix would be incorrect. + // E.g., + // ab + // acab + // Longest matching block is "ab", but if common prefix is + // stripped, it's "a" (tied with "b"). UNIX(tm) diff does so + // strip, so ends up claiming that ab is changed to acab by + // inserting "ca" in the middle. That's minimal but unintuitive: + // "it's obvious" that someone inserted "ac" at the front. + // Windiff ends up at the same place as diff, but by pairing up + // the unique 'b's and then matching the first two 'a's. + besti, bestj, bestsize := alo, blo, 0 + + // find longest junk-free match + // during an iteration of the loop, j2len[j] = length of longest + // junk-free match ending with a[i-1] and b[j] + j2len := map[int]int{} + for i := alo; i != ahi; i++ { + // look at all instances of a[i] in b; note that because + // b2j has no junk keys, the loop is skipped if a[i] is junk + newj2len := map[int]int{} + for _, j := range m.b2j[m.a[i]] { + // a[i] matches b[j] + if j < blo { + continue + } + if j >= bhi { + break + } + k := j2len[j-1] + 1 + newj2len[j] = k + if k > bestsize { + besti, bestj, bestsize = i-k+1, j-k+1, k + } + } + j2len = newj2len + } + + // Extend the best by non-junk elements on each end. In particular, + // "popular" non-junk elements aren't in b2j, which greatly speeds + // the inner loop above, but also means "the best" match so far + // doesn't contain any junk *or* popular non-junk elements. + for besti > alo && bestj > blo && !m.isBJunk(m.b[bestj-1]) && + m.a[besti-1] == m.b[bestj-1] { + besti, bestj, bestsize = besti-1, bestj-1, bestsize+1 + } + for besti+bestsize < ahi && bestj+bestsize < bhi && + !m.isBJunk(m.b[bestj+bestsize]) && + m.a[besti+bestsize] == m.b[bestj+bestsize] { + bestsize += 1 + } + + // Now that we have a wholly interesting match (albeit possibly + // empty!), we may as well suck up the matching junk on each + // side of it too. Can't think of a good reason not to, and it + // saves post-processing the (possibly considerable) expense of + // figuring out what to do with it. In the case of an empty + // interesting match, this is clearly the right thing to do, + // because no other kind of match is possible in the regions. + for besti > alo && bestj > blo && m.isBJunk(m.b[bestj-1]) && + m.a[besti-1] == m.b[bestj-1] { + besti, bestj, bestsize = besti-1, bestj-1, bestsize+1 + } + for besti+bestsize < ahi && bestj+bestsize < bhi && + m.isBJunk(m.b[bestj+bestsize]) && + m.a[besti+bestsize] == m.b[bestj+bestsize] { + bestsize += 1 + } + + return Match{A: besti, B: bestj, Size: bestsize} +} + +// Return list of triples describing matching subsequences. +// +// Each triple is of the form (i, j, n), and means that +// a[i:i+n] == b[j:j+n]. The triples are monotonically increasing in +// i and in j. It's also guaranteed that if (i, j, n) and (i', j', n') are +// adjacent triples in the list, and the second is not the last triple in the +// list, then i+n != i' or j+n != j'. IOW, adjacent triples never describe +// adjacent equal blocks. +// +// The last triple is a dummy, (len(a), len(b), 0), and is the only +// triple with n==0. +func (m *SequenceMatcher) GetMatchingBlocks() []Match { + if m.matchingBlocks != nil { + return m.matchingBlocks + } + + var matchBlocks func(alo, ahi, blo, bhi int, matched []Match) []Match + matchBlocks = func(alo, ahi, blo, bhi int, matched []Match) []Match { + match := m.findLongestMatch(alo, ahi, blo, bhi) + i, j, k := match.A, match.B, match.Size + if match.Size > 0 { + if alo < i && blo < j { + matched = matchBlocks(alo, i, blo, j, matched) + } + matched = append(matched, match) + if i+k < ahi && j+k < bhi { + matched = matchBlocks(i+k, ahi, j+k, bhi, matched) + } + } + return matched + } + matched := matchBlocks(0, len(m.a), 0, len(m.b), nil) + + // It's possible that we have adjacent equal blocks in the + // matching_blocks list now. + nonAdjacent := []Match{} + i1, j1, k1 := 0, 0, 0 + for _, b := range matched { + // Is this block adjacent to i1, j1, k1? + i2, j2, k2 := b.A, b.B, b.Size + if i1+k1 == i2 && j1+k1 == j2 { + // Yes, so collapse them -- this just increases the length of + // the first block by the length of the second, and the first + // block so lengthened remains the block to compare against. + k1 += k2 + } else { + // Not adjacent. Remember the first block (k1==0 means it's + // the dummy we started with), and make the second block the + // new block to compare against. + if k1 > 0 { + nonAdjacent = append(nonAdjacent, Match{i1, j1, k1}) + } + i1, j1, k1 = i2, j2, k2 + } + } + if k1 > 0 { + nonAdjacent = append(nonAdjacent, Match{i1, j1, k1}) + } + + nonAdjacent = append(nonAdjacent, Match{len(m.a), len(m.b), 0}) + m.matchingBlocks = nonAdjacent + return m.matchingBlocks +} + +// Return list of 5-tuples describing how to turn a into b. +// +// Each tuple is of the form (tag, i1, i2, j1, j2). The first tuple +// has i1 == j1 == 0, and remaining tuples have i1 == the i2 from the +// tuple preceding it, and likewise for j1 == the previous j2. +// +// The tags are characters, with these meanings: +// +// 'r' (replace): a[i1:i2] should be replaced by b[j1:j2] +// +// 'd' (delete): a[i1:i2] should be deleted, j1==j2 in this case. +// +// 'i' (insert): b[j1:j2] should be inserted at a[i1:i1], i1==i2 in this case. +// +// 'e' (equal): a[i1:i2] == b[j1:j2] +func (m *SequenceMatcher) GetOpCodes() []OpCode { + if m.opCodes != nil { + return m.opCodes + } + i, j := 0, 0 + matching := m.GetMatchingBlocks() + opCodes := make([]OpCode, 0, len(matching)) + for _, m := range matching { + // invariant: we've pumped out correct diffs to change + // a[:i] into b[:j], and the next matching block is + // a[ai:ai+size] == b[bj:bj+size]. So we need to pump + // out a diff to change a[i:ai] into b[j:bj], pump out + // the matching block, and move (i,j) beyond the match + ai, bj, size := m.A, m.B, m.Size + tag := byte(0) + if i < ai && j < bj { + tag = 'r' + } else if i < ai { + tag = 'd' + } else if j < bj { + tag = 'i' + } + if tag > 0 { + opCodes = append(opCodes, OpCode{tag, i, ai, j, bj}) + } + i, j = ai+size, bj+size + // the list of matching blocks is terminated by a + // sentinel with size 0 + if size > 0 { + opCodes = append(opCodes, OpCode{'e', ai, i, bj, j}) + } + } + m.opCodes = opCodes + return m.opCodes +} + +// Isolate change clusters by eliminating ranges with no changes. +// +// Return a generator of groups with up to n lines of context. +// Each group is in the same format as returned by GetOpCodes(). +func (m *SequenceMatcher) GetGroupedOpCodes(n int) [][]OpCode { + if n < 0 { + n = 3 + } + codes := m.GetOpCodes() + if len(codes) == 0 { + codes = []OpCode{OpCode{'e', 0, 1, 0, 1}} + } + // Fixup leading and trailing groups if they show no changes. + if codes[0].Tag == 'e' { + c := codes[0] + i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2 + codes[0] = OpCode{c.Tag, max(i1, i2-n), i2, max(j1, j2-n), j2} + } + if codes[len(codes)-1].Tag == 'e' { + c := codes[len(codes)-1] + i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2 + codes[len(codes)-1] = OpCode{c.Tag, i1, min(i2, i1+n), j1, min(j2, j1+n)} + } + nn := n + n + groups := [][]OpCode{} + group := []OpCode{} + for _, c := range codes { + i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2 + // End the current group and start a new one whenever + // there is a large range with no changes. + if c.Tag == 'e' && i2-i1 > nn { + group = append(group, OpCode{c.Tag, i1, min(i2, i1+n), + j1, min(j2, j1+n)}) + groups = append(groups, group) + group = []OpCode{} + i1, j1 = max(i1, i2-n), max(j1, j2-n) + } + group = append(group, OpCode{c.Tag, i1, i2, j1, j2}) + } + if len(group) > 0 && !(len(group) == 1 && group[0].Tag == 'e') { + groups = append(groups, group) + } + return groups +} + +// Return a measure of the sequences' similarity (float in [0,1]). +// +// Where T is the total number of elements in both sequences, and +// M is the number of matches, this is 2.0*M / T. +// Note that this is 1 if the sequences are identical, and 0 if +// they have nothing in common. +// +// .Ratio() is expensive to compute if you haven't already computed +// .GetMatchingBlocks() or .GetOpCodes(), in which case you may +// want to try .QuickRatio() or .RealQuickRation() first to get an +// upper bound. +func (m *SequenceMatcher) Ratio() float64 { + matches := 0 + for _, m := range m.GetMatchingBlocks() { + matches += m.Size + } + return calculateRatio(matches, len(m.a)+len(m.b)) +} + +// Return an upper bound on ratio() relatively quickly. +// +// This isn't defined beyond that it is an upper bound on .Ratio(), and +// is faster to compute. +func (m *SequenceMatcher) QuickRatio() float64 { + // viewing a and b as multisets, set matches to the cardinality + // of their intersection; this counts the number of matches + // without regard to order, so is clearly an upper bound + if m.fullBCount == nil { + m.fullBCount = map[string]int{} + for _, s := range m.b { + m.fullBCount[s] = m.fullBCount[s] + 1 + } + } + + // avail[x] is the number of times x appears in 'b' less the + // number of times we've seen it in 'a' so far ... kinda + avail := map[string]int{} + matches := 0 + for _, s := range m.a { + n, ok := avail[s] + if !ok { + n = m.fullBCount[s] + } + avail[s] = n - 1 + if n > 0 { + matches += 1 + } + } + return calculateRatio(matches, len(m.a)+len(m.b)) +} + +// Return an upper bound on ratio() very quickly. +// +// This isn't defined beyond that it is an upper bound on .Ratio(), and +// is faster to compute than either .Ratio() or .QuickRatio(). +func (m *SequenceMatcher) RealQuickRatio() float64 { + la, lb := len(m.a), len(m.b) + return calculateRatio(min(la, lb), la+lb) +} + +// Convert range to the "ed" format +func formatRangeUnified(start, stop int) string { + // Per the diff spec at http://www.unix.org/single_unix_specification/ + beginning := start + 1 // lines start numbering with one + length := stop - start + if length == 1 { + return fmt.Sprintf("%d", beginning) + } + if length == 0 { + beginning -= 1 // empty ranges begin at line just before the range + } + return fmt.Sprintf("%d,%d", beginning, length) +} + +// Unified diff parameters +type UnifiedDiff struct { + A []string // First sequence lines + FromFile string // First file name + FromDate string // First file time + B []string // Second sequence lines + ToFile string // Second file name + ToDate string // Second file time + Eol string // Headers end of line, defaults to LF + Context int // Number of context lines +} + +// Compare two sequences of lines; generate the delta as a unified diff. +// +// Unified diffs are a compact way of showing line changes and a few +// lines of context. The number of context lines is set by 'n' which +// defaults to three. +// +// By default, the diff control lines (those with ---, +++, or @@) are +// created with a trailing newline. This is helpful so that inputs +// created from file.readlines() result in diffs that are suitable for +// file.writelines() since both the inputs and outputs have trailing +// newlines. +// +// For inputs that do not have trailing newlines, set the lineterm +// argument to "" so that the output will be uniformly newline free. +// +// The unidiff format normally has a header for filenames and modification +// times. Any or all of these may be specified using strings for +// 'fromfile', 'tofile', 'fromfiledate', and 'tofiledate'. +// The modification times are normally expressed in the ISO 8601 format. +func WriteUnifiedDiff(writer io.Writer, diff UnifiedDiff) error { + buf := bufio.NewWriter(writer) + defer buf.Flush() + w := func(format string, args ...interface{}) error { + _, err := buf.WriteString(fmt.Sprintf(format, args...)) + return err + } + + if len(diff.Eol) == 0 { + diff.Eol = "\n" + } + + started := false + m := NewMatcher(diff.A, diff.B) + for _, g := range m.GetGroupedOpCodes(diff.Context) { + if !started { + started = true + fromDate := "" + if len(diff.FromDate) > 0 { + fromDate = "\t" + diff.FromDate + } + toDate := "" + if len(diff.ToDate) > 0 { + toDate = "\t" + diff.ToDate + } + err := w("--- %s%s%s", diff.FromFile, fromDate, diff.Eol) + if err != nil { + return err + } + err = w("+++ %s%s%s", diff.ToFile, toDate, diff.Eol) + if err != nil { + return err + } + } + first, last := g[0], g[len(g)-1] + range1 := formatRangeUnified(first.I1, last.I2) + range2 := formatRangeUnified(first.J1, last.J2) + if err := w("@@ -%s +%s @@%s", range1, range2, diff.Eol); err != nil { + return err + } + for _, c := range g { + i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2 + if c.Tag == 'e' { + for _, line := range diff.A[i1:i2] { + if err := w(" " + line); err != nil { + return err + } + } + continue + } + if c.Tag == 'r' || c.Tag == 'd' { + for _, line := range diff.A[i1:i2] { + if err := w("-" + line); err != nil { + return err + } + } + } + if c.Tag == 'r' || c.Tag == 'i' { + for _, line := range diff.B[j1:j2] { + if err := w("+" + line); err != nil { + return err + } + } + } + } + } + return nil +} + +// Like WriteUnifiedDiff but returns the diff a string. +func GetUnifiedDiffString(diff UnifiedDiff) (string, error) { + w := &bytes.Buffer{} + err := WriteUnifiedDiff(w, diff) + return string(w.Bytes()), err +} + +// Convert range to the "ed" format. +func formatRangeContext(start, stop int) string { + // Per the diff spec at http://www.unix.org/single_unix_specification/ + beginning := start + 1 // lines start numbering with one + length := stop - start + if length == 0 { + beginning -= 1 // empty ranges begin at line just before the range + } + if length <= 1 { + return fmt.Sprintf("%d", beginning) + } + return fmt.Sprintf("%d,%d", beginning, beginning+length-1) +} + +type ContextDiff UnifiedDiff + +// Compare two sequences of lines; generate the delta as a context diff. +// +// Context diffs are a compact way of showing line changes and a few +// lines of context. The number of context lines is set by diff.Context +// which defaults to three. +// +// By default, the diff control lines (those with *** or ---) are +// created with a trailing newline. +// +// For inputs that do not have trailing newlines, set the diff.Eol +// argument to "" so that the output will be uniformly newline free. +// +// The context diff format normally has a header for filenames and +// modification times. Any or all of these may be specified using +// strings for diff.FromFile, diff.ToFile, diff.FromDate, diff.ToDate. +// The modification times are normally expressed in the ISO 8601 format. +// If not specified, the strings default to blanks. +func WriteContextDiff(writer io.Writer, diff ContextDiff) error { + buf := bufio.NewWriter(writer) + defer buf.Flush() + var diffErr error + w := func(format string, args ...interface{}) { + _, err := buf.WriteString(fmt.Sprintf(format, args...)) + if diffErr == nil && err != nil { + diffErr = err + } + } + + if len(diff.Eol) == 0 { + diff.Eol = "\n" + } + + prefix := map[byte]string{ + 'i': "+ ", + 'd': "- ", + 'r': "! ", + 'e': " ", + } + + started := false + m := NewMatcher(diff.A, diff.B) + for _, g := range m.GetGroupedOpCodes(diff.Context) { + if !started { + started = true + fromDate := "" + if len(diff.FromDate) > 0 { + fromDate = "\t" + diff.FromDate + } + toDate := "" + if len(diff.ToDate) > 0 { + toDate = "\t" + diff.ToDate + } + w("*** %s%s%s", diff.FromFile, fromDate, diff.Eol) + w("--- %s%s%s", diff.ToFile, toDate, diff.Eol) + } + + first, last := g[0], g[len(g)-1] + w("***************" + diff.Eol) + + range1 := formatRangeContext(first.I1, last.I2) + w("*** %s ****%s", range1, diff.Eol) + for _, c := range g { + if c.Tag == 'r' || c.Tag == 'd' { + for _, cc := range g { + if cc.Tag == 'i' { + continue + } + for _, line := range diff.A[cc.I1:cc.I2] { + w(prefix[cc.Tag] + line) + } + } + break + } + } + + range2 := formatRangeContext(first.J1, last.J2) + w("--- %s ----%s", range2, diff.Eol) + for _, c := range g { + if c.Tag == 'r' || c.Tag == 'i' { + for _, cc := range g { + if cc.Tag == 'd' { + continue + } + for _, line := range diff.B[cc.J1:cc.J2] { + w(prefix[cc.Tag] + line) + } + } + break + } + } + } + return diffErr +} + +// Like WriteContextDiff but returns the diff a string. +func GetContextDiffString(diff ContextDiff) (string, error) { + w := &bytes.Buffer{} + err := WriteContextDiff(w, diff) + return string(w.Bytes()), err +} + +// Split a string on "\n" while preserving them. The output can be used +// as input for UnifiedDiff and ContextDiff structures. +func SplitLines(s string) []string { + lines := strings.SplitAfter(s, "\n") + lines[len(lines)-1] += "\n" + return lines +} |