[chromium-reviews] Add Compact Language Detection (CLD) library to Chrome. This works in Windows...

third_party/cld/bar/toolbar/cld/i18n/encodings/compact_lang_det/subsetsequence.cc

Index: third_party/cld/bar/toolbar/cld/i18n/encodings/compact_lang_det/subsetsequence.cc
===================================================================
--- third_party/cld/bar/toolbar/cld/i18n/encodings/compact_lang_det/subsetsequence.cc	(revision 0)
+++ third_party/cld/bar/toolbar/cld/i18n/encodings/compact_lang_det/subsetsequence.cc	(revision 0)
@@ -0,0 +1,259 @@
+// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Remember a subset of a sequence of values, using a modest amount of memory
+
+/***
+  Design:
+  Accumulate in powers of three, using 3-way median to collapse entries.
+  At any given time, there is one most-dense (highest power of 3) range of
+  entries and a series of less-dense ranges that hold 0..2 entries each. There
+  is a bounded-size storage array of S cells for all the entries.
+
+  The overflow detect is set up so that a new higher power of 3, K+1, is
+  triggered precisely when range K has 3n entries and all ranges < K have
+  zero entries.
+
+  In general, think of the range sizes as a multi-digit base 3 number, except
+  the highest digit may exceed 2:
+
+  3**6  3**5  3**4  3**3  3**2  3**1  3**0  K=2
+    0     0     0     0   3n-1    2     2   unused:1
+
+  There are a total of 3n-1 + 2 + 2 entries in use. Assume a size limit S at
+  one more than that, and we add a new 3**0 entry and "carry" by performing
+  medians on any group of 3 elements:
+
+  3**6  3**5  3**4  3**3  3**2  3**1  3**0       K=2
+    0     0     0     0   3n-1    2     3        unused:0
+    0     0     0     0   3n-1    3     0 carry  unused:2
+    0     0     0     0    3n     0     0 carry  unused:4
+
+  To accumulate 2 entries at all levels < K and 3 just before the first carry at
+  level 0, we need 2*K + 1 unused cells after doing all carries, or five cells
+  in this case. Since we only have 4 cells in the example above, we need to
+  make room by starting a new power of three:
+
+  3**6  3**5  3**4  3**3  3**2  3**1  3**0
+    0     0     0     0    3n     0     0        K=2 unused:4
+    0     0     0     n     0     0     0        K=3 unused:2n+4
+
+  In the code below, we don't worry about overflow from the topmost place.
+
+
+***/
+
+#include "third_party/cld/bar/toolbar/cld/i18n/encodings/compact_lang_det/subsetsequence.h"
+#include <stdio.h>
+
+#include "third_party/cld/bar/toolbar/cld/i18n/encodings/compact_lang_det/win/cld_logging.h"
+
+void DumpInts(const char* label, const int* v, int n) {
+  printf("%s ", label);
+  for (int i = 0; i < n; ++i) {
+    printf("%d ", v[i]);
+  }
+  printf("\n");
+}
+
+void DumpUint8s(const char* label, const uint8* v, int n) {
+  printf("%s ", label);
+  for (int i = 0; i < n; ++i) {
+    printf("%d ", v[i]);
+  }
+  printf("\n");
+}
+
+// Return median of seq_[sub] .. seq_[sub+2], favoring middle element
+uint8 SubsetSequence::Median3(int sub) {
+  if (seq_[sub] == seq_[sub + 1]) {
+    return seq_[sub];
+  }
+  if (seq_[sub] == seq_[sub + 2]) {
+    return seq_[sub];
+  }
+  return seq_[sub + 1];
+}
+
+void SubsetSequence::Init() {
+  // printf("Init\n");
+
+  k_ = 0;
+  count_[0] = 0;
+  next_e_ = 0;
+  seq_[0] = 0;    // Default value if no calls to Add
+
+  // Want largest <= kMaxSeq_ that allows reserve and makes count_[k_] = 0 mod 3
+  int reserve = (2 * k_ + 1);
+  level_limit_e_ = kMaxSeq_ - reserve;
+  level_limit_e_ = (level_limit_e_ / 3) * 3;  // Round down to multiple of 3
+  limit_e_ = level_limit_e_;
+}
+
+// Compress level k by 3x, creating level k+1
+void SubsetSequence::NewLevel() {
+  // printf("NewLevel 3 ** %d\n", k_ + 1);
+  //DumpUint8s("count[k]", count_, k_ + 1);
+  //DumpUint8s("seq[next]", seq_, next_e_);
+
+  // Incoming level must be an exact multiple of three in size
+  CHECK((count_[k_] % 3) == 0);
+  int k_size = count_[k_];
+  int new_size = k_size / 3;
+
+  // Compress down by 3x, via median
+  for (int j = 0; j < new_size; ++j) {
+    seq_[j] = Median3(j * 3);
+  }
+
+  // Update counts
+  count_[k_] = 0;
+  // Else Overflow -- just continue with 3x dense Level K
+  if (k_ < (kMaxLevel_ - 1)) {++k_;}
+  count_[k_] = new_size;
+
+  // Update limits
+  next_e_ = new_size;
+  limit_e_ = next_e_ + 3;
+
+  // Want largest <= kMaxSeq_ that allows reserve and makes count_[k_] = 0 mod 3
+  int reserve = (2 * k_ + 1);
+  level_limit_e_ = kMaxSeq_ - reserve;
+  level_limit_e_ = (level_limit_e_ / 3) * 3;  // Round down to multiple of 3
+                                              //
+  //DumpUint8s("after: count[k]", count_, k_ + 1);
+  //DumpUint8s("after: seq[next]", seq_, next_e_);
+}
+
+void SubsetSequence::DoCarries() {
+  CHECK(count_[k_] > 3);    // We depend on count_[k_] being > 3 to stop while
+  // Make room by carrying
+
+  //DumpUint8s("DoCarries count[k]", count_, k_ + 1);
+  //DumpUint8s("DoCarries seq[next]", seq_, next_e_);
+
+  int i = 0;
+  while (count_[i] == 3) {
+    next_e_ -= 3;
+    seq_[next_e_] = Median3(next_e_);
+    ++next_e_;
+    count_[i] = 0;
+    ++count_[i + 1];
+    ++i;
+  }
+  limit_e_ = next_e_ + 3;
+
+  //DumpUint8s("after: DoCarries count[k]", count_, k_ + 1);
+  //DumpUint8s("after: DoCarries seq[next]", seq_, next_e_);
+
+  // If we just fully carried into level K,
+  // Make sure there is now enough room, else start level K + 1
+  if (i >= k_) {
+    CHECK(count_[k_] == next_e_);
+    if (next_e_ >= level_limit_e_) {
+      NewLevel();
+    }
+  }
+}
+
+void SubsetSequence::Add(uint8 e) {
+  // Add an entry then carry as needed
+  seq_[next_e_] = e;
+  ++next_e_;
+  ++count_[0];
+
+  if (next_e_ >= limit_e_) {
+    DoCarries();
+  }
+}
+
+
+// Collapse tail end by simple median across disparate-weight values,
+// dropping or duplicating last value if need be.
+// This routine is idempotent.
+void SubsetSequence::Flush() {
+  // printf("Flush %d\n", count_[k_]);
+  int start_tail = count_[k_];
+  int size_tail = next_e_ - start_tail;
+  if ((size_tail % 3) == 2) {
+    seq_[next_e_] = seq_[next_e_ - 1];      // Duplicate last value
+    ++size_tail;
+  }
+
+  // Compress tail down by 3x, via median
+  int new_size = size_tail / 3;             // May delete last value
+  for (int j = 0; j < new_size; ++j) {
+    seq_[start_tail + j] = Median3(start_tail + j * 3);
+  }
+
+  next_e_ = start_tail + new_size;
+  count_[k_] = next_e_;
+}
+
+
+// Extract representative pattern of exactly N values into dst[0..n-1]
+// This routine may be called multiple times, but it may downsample as a
+// side effect, causing subsequent calls with larger N to get poor answers.
+void SubsetSequence::Extract(int to_n, uint8* dst) {
+  // Collapse partial-carries in tail
+  Flush();
+
+  // Just use Bresenham to resample
+  int from_n = next_e_;
+  if (to_n >= from_n) {
+    // Up-sample from_n => to_n
+    int err = to_n - 1;          // bias toward no overshoot
+    int j = 0;
+    for (int i = 0; i < to_n; ++i) {
+      dst[i] = seq_[j];
+      err -= from_n;
+      if (err < 0) {
+        ++j;
+        err += to_n;
+      }
+    }
+  } else {
+    // Get to the point that the number of samples is <= 3 * to_n
+    while (next_e_ > (to_n * 3)) {
+      // Compress down by 3x, via median
+      // printf("Extract, median %d / 3\n", next_e_);
+      if ((next_e_ % 3) == 2) {
+        seq_[next_e_] = seq_[next_e_ - 1];    // Duplicate last value
+        ++next_e_;
+      }
+      int new_size = next_e_ / 3;             // May delete last value
+      for (int j = 0; j < new_size; ++j) {
+        seq_[j] = Median3(j * 3);
+      }
+      next_e_ = new_size;
+      count_[k_] = next_e_;
+    }
+    from_n = next_e_;
+
+    if (to_n == from_n) {
+      // Copy verbatim
+      for (int i = 0; i < to_n; ++i) {
+        dst[i] = seq_[i];
+      }
+      return;
+    }
+
+    // Down-sample from_n => to_n, using medians
+    int err = 0;          // Bias to immediate median sample
+    int j = 0;
+    for (int i = 0; i < from_n; ++i) {
+      err -= to_n;
+      if (err < 0) {
+        if (i <= (next_e_ - 2)) {
+          dst[j] = Median3(i);
+        } else {
+          dst[j] = seq_[i];
+        }
+        ++j;
+        err += from_n;
+      }
+    }
+  }
+
+}
Property changes on: third_party\cld\bar\toolbar\cld\i18n\encodings\compact_lang_det\subsetsequence.cc
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Added: svn:eol-style
   + LF