diff --git a/BUILD b/BUILD
index 6265b71..72781d7 100644
--- a/BUILD
+++ b/BUILD
@@ -83,6 +83,7 @@
     "-Wmissing-declarations",
     "-Wmissing-prototypes",
     "-Wno-strict-aliasing",
+    "-Wno-implicit-fallthrough",
     "-Wshadow",
     "-Wsign-compare",
 ]
diff --git a/c/enc/backward_references.c b/c/enc/backward_references.c
index 62ecea7..3dd897b 100644
--- a/c/enc/backward_references.c
+++ b/c/enc/backward_references.c
@@ -49,6 +49,7 @@
 #define CAT(a, b) a ## b
 #define FN(X) EXPAND_CAT(X, HASHER())
 #define EXPORT_FN(X) EXPAND_CAT(X, EXPAND_CAT(PREFIX(), HASHER()))
+
 #define PREFIX() N
 
 #define HASHER() H2
@@ -97,6 +98,7 @@
 #undef HASHER
 
 #undef PREFIX
+
 #undef EXPORT_FN
 #undef FN
 #undef CAT
diff --git a/c/enc/backward_references_hq.c b/c/enc/backward_references_hq.c
index 62c6ba2..e7486c4 100644
--- a/c/enc/backward_references_hq.c
+++ b/c/enc/backward_references_hq.c
@@ -76,7 +76,7 @@
   /* The insert and copy length symbols. */
   float cost_cmd_[BROTLI_NUM_COMMAND_SYMBOLS];
   float* cost_dist_;
-  uint32_t distance_alphabet_size;
+  uint32_t distance_histogram_size;
   /* Cumulative costs of literals per position in the stream. */
   float* literal_costs_;
   float min_cost_cmd_;
@@ -86,10 +86,14 @@
 static void InitZopfliCostModel(
     MemoryManager* m, ZopfliCostModel* self, const BrotliDistanceParams* dist,
     size_t num_bytes) {
+  uint32_t distance_histogram_size = dist->alphabet_size;
+  if (distance_histogram_size > BROTLI_MAX_EFFECTIVE_DISTANCE_ALPHABET_SIZE) {
+    distance_histogram_size = BROTLI_MAX_EFFECTIVE_DISTANCE_ALPHABET_SIZE;
+  }
   self->num_bytes_ = num_bytes;
   self->literal_costs_ = BROTLI_ALLOC(m, float, num_bytes + 2);
   self->cost_dist_ = BROTLI_ALLOC(m, float, dist->alphabet_size);
-  self->distance_alphabet_size = dist->alphabet_size;
+  self->distance_histogram_size = distance_histogram_size;
   if (BROTLI_IS_OOM(m)) return;
 }
 
@@ -171,7 +175,7 @@
           cost_literal);
   SetCost(histogram_cmd, BROTLI_NUM_COMMAND_SYMBOLS, BROTLI_FALSE,
           cost_cmd);
-  SetCost(histogram_dist, self->distance_alphabet_size, BROTLI_FALSE,
+  SetCost(histogram_dist, self->distance_histogram_size, BROTLI_FALSE,
           self->cost_dist_);
 
   for (i = 0; i < BROTLI_NUM_COMMAND_SYMBOLS; ++i) {
@@ -214,7 +218,7 @@
   for (i = 0; i < BROTLI_NUM_COMMAND_SYMBOLS; ++i) {
     cost_cmd[i] = (float)FastLog2(11 + (uint32_t)i);
   }
-  for (i = 0; i < self->distance_alphabet_size; ++i) {
+  for (i = 0; i < self->distance_histogram_size; ++i) {
     cost_dist[i] = (float)FastLog2(20 + (uint32_t)i);
   }
   self->min_cost_cmd_ = (float)FastLog2(11);
diff --git a/c/enc/encode.c b/c/enc/encode.c
index 563c827..623b88f 100644
--- a/c/enc/encode.c
+++ b/c/enc/encode.c
@@ -167,6 +167,14 @@
       state->params.large_window = TO_BROTLI_BOOL(!!value);
       return BROTLI_TRUE;
 
+    case BROTLI_PARAM_NPOSTFIX:
+      state->params.dist.distance_postfix_bits = value;
+      return BROTLI_TRUE;
+
+    case BROTLI_PARAM_NDIRECT:
+      state->params.dist.num_direct_distance_codes = value;
+      return BROTLI_TRUE;
+
     default: return BROTLI_FALSE;
   }
 }
@@ -636,26 +644,42 @@
 }
 
 static void ChooseDistanceParams(BrotliEncoderParams* params) {
-  /* NDIRECT, NPOSTFIX must be both zero for qualities
-     up to MIN_QUALITY_FOR_BLOCK_SPLIT == 3. */
-  uint32_t num_direct_distance_codes = 0;
   uint32_t distance_postfix_bits = 0;
+  uint32_t num_direct_distance_codes = 0;
   uint32_t alphabet_size;
   size_t max_distance = BROTLI_MAX_DISTANCE;
 
-  if (params->quality >= MIN_QUALITY_FOR_RECOMPUTE_DISTANCE_PREFIXES &&
-      params->mode == BROTLI_MODE_FONT) {
-    num_direct_distance_codes = 12;
-    distance_postfix_bits = 1;
-    max_distance = (1U << 27) + 4;
+  if (params->quality >= MIN_QUALITY_FOR_NONZERO_DISTANCE_PARAMS) {
+    uint32_t ndirect_msb;
+    if (params->mode == BROTLI_MODE_FONT) {
+      distance_postfix_bits = 1;
+      num_direct_distance_codes = 12;
+    } else {
+      distance_postfix_bits = params->dist.distance_postfix_bits;
+      num_direct_distance_codes = params->dist.num_direct_distance_codes;
+    }
+    ndirect_msb = (num_direct_distance_codes >> distance_postfix_bits) & 0x0F;
+    if (distance_postfix_bits > BROTLI_MAX_NPOSTFIX ||
+        num_direct_distance_codes > BROTLI_MAX_NDIRECT ||
+        (ndirect_msb << distance_postfix_bits) != num_direct_distance_codes) {
+      distance_postfix_bits = 0;
+      num_direct_distance_codes = 0;
+    }
+    max_distance = num_direct_distance_codes +
+        (1U << (BROTLI_MAX_DISTANCE_BITS + distance_postfix_bits + 2)) -
+        (1U << (distance_postfix_bits + 2));
   }
 
   alphabet_size = BROTLI_DISTANCE_ALPHABET_SIZE(
       num_direct_distance_codes, distance_postfix_bits,
       BROTLI_MAX_DISTANCE_BITS);
   if (params->large_window) {
-    max_distance = BROTLI_MAX_ALLOWED_DISTANCE;
-    if (num_direct_distance_codes != 0 || distance_postfix_bits != 0) {
+    /* The maximum distance is set so that no distance symbol used can encode
+       a distance larger than BROTLI_MAX_ALLOWED_DISTANCE with all
+       its extra bits set. */
+    const uint32_t bound_ndirect[BROTLI_MAX_NDIRECT + 1] = {1, 6, 16, 36};
+    max_distance = (1U << 31) - 32;
+    if (num_direct_distance_codes >= bound_ndirect[distance_postfix_bits]) {
       max_distance = (3U << 29) - 4;
     }
     alphabet_size = BROTLI_DISTANCE_ALPHABET_SIZE(
@@ -663,8 +687,8 @@
         BROTLI_LARGE_MAX_DISTANCE_BITS);
   }
 
-  params->dist.num_direct_distance_codes = num_direct_distance_codes;
   params->dist.distance_postfix_bits = distance_postfix_bits;
+  params->dist.num_direct_distance_codes = num_direct_distance_codes;
   params->dist.alphabet_size = alphabet_size;
   params->dist.max_distance = max_distance;
 }
@@ -710,8 +734,8 @@
   params->size_hint = 0;
   params->disable_literal_context_modeling = BROTLI_FALSE;
   BrotliInitEncoderDictionary(&params->dictionary);
-  params->dist.num_direct_distance_codes = 0;
   params->dist.distance_postfix_bits = 0;
+  params->dist.num_direct_distance_codes = 0;
   params->dist.alphabet_size =
       BROTLI_DISTANCE_ALPHABET_SIZE(0, 0, BROTLI_MAX_DISTANCE_BITS);
   params->dist.max_distance = BROTLI_MAX_DISTANCE;
diff --git a/c/enc/memory.h b/c/enc/memory.h
index 2d56e97..ab928d0 100644
--- a/c/enc/memory.h
+++ b/c/enc/memory.h
@@ -80,6 +80,21 @@
   }                                              \
 }
 
+/*
+Appends value and dynamically grows array capacity when needed
+M: MemoryManager
+T: data type
+A: array
+C: array capacity
+S: array size
+V: value to append
+*/
+#define BROTLI_ENSURE_CAPACITY_APPEND(M, T, A, C, S, V) { \
+  (S)++;                                                  \
+  BROTLI_ENSURE_CAPACITY(M, T, A, C, S);                  \
+  A[(S) - 1] = (V);                                       \
+}
+
 #if defined(__cplusplus) || defined(c_plusplus)
 }  /* extern "C" */
 #endif
diff --git a/c/enc/params.h b/c/enc/params.h
index 9bcf236..6ecf1d3 100755
--- a/c/enc/params.h
+++ b/c/enc/params.h
@@ -21,8 +21,8 @@
 } BrotliHasherParams;
 
 typedef struct BrotliDistanceParams {
-  uint32_t num_direct_distance_codes;
   uint32_t distance_postfix_bits;
+  uint32_t num_direct_distance_codes;
   uint32_t alphabet_size;
   size_t max_distance;
 } BrotliDistanceParams;
diff --git a/c/enc/quality.h b/c/enc/quality.h
index f9b1111..aa7ba0d 100644
--- a/c/enc/quality.h
+++ b/c/enc/quality.h
@@ -21,13 +21,12 @@
 
 #define MAX_QUALITY_FOR_STATIC_ENTROPY_CODES 2
 #define MIN_QUALITY_FOR_BLOCK_SPLIT 4
+#define MIN_QUALITY_FOR_NONZERO_DISTANCE_PARAMS 4
 #define MIN_QUALITY_FOR_OPTIMIZE_HISTOGRAMS 4
 #define MIN_QUALITY_FOR_EXTENSIVE_REFERENCE_SEARCH 5
 #define MIN_QUALITY_FOR_CONTEXT_MODELING 5
 #define MIN_QUALITY_FOR_HQ_CONTEXT_MODELING 7
 #define MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING 10
-/* Only for "font" mode. */
-#define MIN_QUALITY_FOR_RECOMPUTE_DISTANCE_PREFIXES 10
 
 /* For quality below MIN_QUALITY_FOR_BLOCK_SPLIT there is no block splitting,
    so we buffer at most this much literals and commands. */
diff --git a/c/include/brotli/encode.h b/c/include/brotli/encode.h
index 0b5c8c7..0ced7e5 100644
--- a/c/include/brotli/encode.h
+++ b/c/include/brotli/encode.h
@@ -185,7 +185,23 @@
   /**
    * Flag that determines if "Large Window Brotli" is used.
    */
-  BROTLI_PARAM_LARGE_WINDOW = 6
+  BROTLI_PARAM_LARGE_WINDOW = 6,
+  /**
+   * Recommended number of postfix bits (NPOSTFIX).
+   *
+   * Encoder may change this value.
+   *
+   * Range is from 0 to ::BROTLI_MAX_NPOSTFIX.
+   */
+  BROTLI_PARAM_NPOSTFIX = 7,
+  /**
+   * Recommended number of direct distance codes (NDIRECT).
+   *
+   * Encoder may change this value.
+   *
+   * Range is from 0 to (15 << NPOSTFIX) in steps of (1 << NPOSTFIX).
+   */
+  BROTLI_PARAM_NDIRECT = 8
 } BrotliEncoderParameter;
 
 /**
diff --git a/c/tools/brotli.c b/c/tools/brotli.c
index 2abfc27..17a3bb6 100644
--- a/c/tools/brotli.c
+++ b/c/tools/brotli.c
@@ -195,6 +195,7 @@
        This check is an additional guard that is never triggered, but provides
        a guard for future changes. */
     if (next_option_index > (MAX_OPTIONS - 2)) {
+      fprintf(stderr, "too many options passed\n");
       return COMMAND_INVALID;
     }
 
@@ -220,80 +221,135 @@
       for (j = 1; j < arg_len; ++j) {
         char c = arg[j];
         if (c >= '0' && c <= '9') {
-          if (quality_set) return COMMAND_INVALID;
+          if (quality_set) {
+            fprintf(stderr, "quality already set\n");
+            return COMMAND_INVALID;
+          }
           quality_set = BROTLI_TRUE;
           params->quality = c - '0';
           continue;
         } else if (c == 'c') {
-          if (output_set) return COMMAND_INVALID;
+          if (output_set) {
+            fprintf(stderr, "write to standard output already set\n");
+            return COMMAND_INVALID;
+          }
           output_set = BROTLI_TRUE;
           params->write_to_stdout = BROTLI_TRUE;
           continue;
         } else if (c == 'd') {
-          if (command_set) return COMMAND_INVALID;
+          if (command_set) {
+            fprintf(stderr, "command already set when parsing -d\n");
+            return COMMAND_INVALID;
+          }
           command_set = BROTLI_TRUE;
           command = COMMAND_DECOMPRESS;
           continue;
         } else if (c == 'f') {
-          if (params->force_overwrite) return COMMAND_INVALID;
+          if (params->force_overwrite) {
+            fprintf(stderr, "force output overwrite already set\n");
+            return COMMAND_INVALID;
+          }
           params->force_overwrite = BROTLI_TRUE;
           continue;
         } else if (c == 'h') {
           /* Don't parse further. */
           return COMMAND_HELP;
         } else if (c == 'j' || c == 'k') {
-          if (keep_set) return COMMAND_INVALID;
+          if (keep_set) {
+            fprintf(stderr, "argument --rm / -j or --keep / -n already set\n");
+            return COMMAND_INVALID;
+          }
           keep_set = BROTLI_TRUE;
           params->junk_source = TO_BROTLI_BOOL(c == 'j');
           continue;
         } else if (c == 'n') {
-          if (!params->copy_stat) return COMMAND_INVALID;
+          if (!params->copy_stat) {
+            fprintf(stderr, "argument --no-copy-stat / -n already set\n");
+            return COMMAND_INVALID;
+          }
           params->copy_stat = BROTLI_FALSE;
           continue;
         } else if (c == 't') {
-          if (command_set) return COMMAND_INVALID;
+          if (command_set) {
+            fprintf(stderr, "command already set when parsing -t\n");
+            return COMMAND_INVALID;
+          }
           command_set = BROTLI_TRUE;
           command = COMMAND_TEST_INTEGRITY;
           continue;
         } else if (c == 'v') {
-          if (params->verbose) return COMMAND_INVALID;
+          if (params->verbose) {
+            fprintf(stderr, "argument --verbose / -v already set\n");
+            return COMMAND_INVALID;
+          }
           params->verbose = BROTLI_TRUE;
           continue;
         } else if (c == 'V') {
           /* Don't parse further. */
           return COMMAND_VERSION;
         } else if (c == 'Z') {
-          if (quality_set) return COMMAND_INVALID;
+          if (quality_set) {
+            fprintf(stderr, "quality already set\n");
+            return COMMAND_INVALID;
+          }
           quality_set = BROTLI_TRUE;
           params->quality = 11;
           continue;
         }
         /* o/q/w/D/S with parameter is expected */
         if (c != 'o' && c != 'q' && c != 'w' && c != 'D' && c != 'S') {
+          fprintf(stderr, "invalid argument -%c\n", c);
           return COMMAND_INVALID;
         }
-        if (j + 1 != arg_len) return COMMAND_INVALID;
+        if (j + 1 != arg_len) {
+          fprintf(stderr, "expected parameter for argument -%c\n", c);
+          return COMMAND_INVALID;
+        }
         i++;
-        if (i == argc || !argv[i] || argv[i][0] == 0) return COMMAND_INVALID;
+        if (i == argc || !argv[i] || argv[i][0] == 0) {
+          fprintf(stderr, "expected parameter for argument -%c\n", c);
+          return COMMAND_INVALID;
+        }
         params->not_input_indices[next_option_index++] = i;
         if (c == 'o') {
-          if (output_set) return COMMAND_INVALID;
+          if (output_set) {
+            fprintf(stderr, "write to standard output already set (-o)\n");
+            return COMMAND_INVALID;
+          }
           params->output_path = argv[i];
         } else if (c == 'q') {
-          if (quality_set) return COMMAND_INVALID;
+          if (quality_set) {
+            fprintf(stderr, "quality already set\n");
+            return COMMAND_INVALID;
+          }
           quality_set = ParseInt(argv[i], BROTLI_MIN_QUALITY,
                                  BROTLI_MAX_QUALITY, &params->quality);
-          if (!quality_set) return COMMAND_INVALID;
+          if (!quality_set) {
+            fprintf(stderr, "error parsing quality value [%s]\n", argv[i]);
+            return COMMAND_INVALID;
+          }
         } else if (c == 'w') {
-          if (lgwin_set) return COMMAND_INVALID;
+          if (lgwin_set) {
+            fprintf(stderr, "lgwin parameter already set\n");
+            return COMMAND_INVALID;
+          }
           lgwin_set = ParseInt(argv[i], 0,
                                BROTLI_MAX_WINDOW_BITS, &params->lgwin);
-          if (!lgwin_set) return COMMAND_INVALID;
+          if (!lgwin_set) {
+            fprintf(stderr, "error parsing lgwin value [%s]\n", argv[i]);
+            return COMMAND_INVALID;
+          }
           if (params->lgwin != 0 && params->lgwin < BROTLI_MIN_WINDOW_BITS) {
+            fprintf(stderr,
+                    "lgwin parameter (%d) smaller than the minimum (%d)\n",
+                    params->lgwin, BROTLI_MIN_WINDOW_BITS);
             return COMMAND_INVALID;
           }
         } else if (c == 'S') {
-          if (suffix_set) return COMMAND_INVALID;
+          if (suffix_set) {
+            fprintf(stderr, "suffix already set\n");
+            return COMMAND_INVALID;
+          }
           suffix_set = BROTLI_TRUE;
           params->suffix = argv[i];
         }
@@ -301,40 +357,67 @@
     } else {  /* Double-dash. */
       arg = &arg[2];
       if (strcmp("best", arg) == 0) {
-        if (quality_set) return COMMAND_INVALID;
+        if (quality_set) {
+          fprintf(stderr, "quality already set\n");
+          return COMMAND_INVALID;
+        }
         quality_set = BROTLI_TRUE;
         params->quality = 11;
       } else if (strcmp("decompress", arg) == 0) {
-        if (command_set) return COMMAND_INVALID;
+        if (command_set) {
+          fprintf(stderr, "command already set when parsing --decompress\n");
+          return COMMAND_INVALID;
+        }
         command_set = BROTLI_TRUE;
         command = COMMAND_DECOMPRESS;
       } else if (strcmp("force", arg) == 0) {
-        if (params->force_overwrite) return COMMAND_INVALID;
+        if (params->force_overwrite) {
+          fprintf(stderr, "force output overwrite already set\n");
+          return COMMAND_INVALID;
+        }
         params->force_overwrite = BROTLI_TRUE;
       } else if (strcmp("help", arg) == 0) {
         /* Don't parse further. */
         return COMMAND_HELP;
       } else if (strcmp("keep", arg) == 0) {
-        if (keep_set) return COMMAND_INVALID;
+        if (keep_set) {
+          fprintf(stderr, "argument --rm / -j or --keep / -n already set\n");
+          return COMMAND_INVALID;
+        }
         keep_set = BROTLI_TRUE;
         params->junk_source = BROTLI_FALSE;
       } else if (strcmp("no-copy-stat", arg) == 0) {
-        if (!params->copy_stat) return COMMAND_INVALID;
+        if (!params->copy_stat) {
+          fprintf(stderr, "argument --no-copy-stat / -n already set\n");
+          return COMMAND_INVALID;
+        }
         params->copy_stat = BROTLI_FALSE;
       } else if (strcmp("rm", arg) == 0) {
-        if (keep_set) return COMMAND_INVALID;
+        if (keep_set) {
+          fprintf(stderr, "argument --rm / -j or --keep / -n already set\n");
+          return COMMAND_INVALID;
+        }
         keep_set = BROTLI_TRUE;
         params->junk_source = BROTLI_TRUE;
       } else if (strcmp("stdout", arg) == 0) {
-        if (output_set) return COMMAND_INVALID;
+        if (output_set) {
+          fprintf(stderr, "write to standard output already set\n");
+          return COMMAND_INVALID;
+        }
         output_set = BROTLI_TRUE;
         params->write_to_stdout = BROTLI_TRUE;
       } else if (strcmp("test", arg) == 0) {
-        if (command_set) return COMMAND_INVALID;
+        if (command_set) {
+          fprintf(stderr, "command already set when parsing --test\n");
+          return COMMAND_INVALID;
+        }
         command_set = BROTLI_TRUE;
         command = COMMAND_TEST_INTEGRITY;
       } else if (strcmp("verbose", arg) == 0) {
-        if (params->verbose) return COMMAND_INVALID;
+        if (params->verbose) {
+          fprintf(stderr, "argument --verbose / -v already set\n");
+          return COMMAND_INVALID;
+        }
         params->verbose = BROTLI_TRUE;
       } else if (strcmp("version", arg) == 0) {
         /* Don't parse further. */
@@ -343,30 +426,56 @@
         /* key=value */
         const char* value = strrchr(arg, '=');
         size_t key_len;
-        if (!value || value[1] == 0) return COMMAND_INVALID;
+        if (!value || value[1] == 0) {
+          fprintf(stderr, "must pass the parameter as --%s=value\n", arg);
+          return COMMAND_INVALID;
+        }
         key_len = (size_t)(value - arg);
         value++;
         if (strncmp("lgwin", arg, key_len) == 0) {
-          if (lgwin_set) return COMMAND_INVALID;
+          if (lgwin_set) {
+            fprintf(stderr, "lgwin parameter already set\n");
+            return COMMAND_INVALID;
+          }
           lgwin_set = ParseInt(value, 0,
                                BROTLI_MAX_WINDOW_BITS, &params->lgwin);
-          if (!lgwin_set) return COMMAND_INVALID;
+          if (!lgwin_set) {
+            fprintf(stderr, "error parsing lgwin value [%s]\n", value);
+            return COMMAND_INVALID;
+          }
           if (params->lgwin != 0 && params->lgwin < BROTLI_MIN_WINDOW_BITS) {
+            fprintf(stderr,
+                    "lgwin parameter (%d) smaller than the minimum (%d)\n",
+                    params->lgwin, BROTLI_MIN_WINDOW_BITS);
             return COMMAND_INVALID;
           }
         } else if (strncmp("output", arg, key_len) == 0) {
-          if (output_set) return COMMAND_INVALID;
+          if (output_set) {
+            fprintf(stderr,
+                    "write to standard output already set (--output)\n");
+            return COMMAND_INVALID;
+          }
           params->output_path = value;
         } else if (strncmp("quality", arg, key_len) == 0) {
-          if (quality_set) return COMMAND_INVALID;
+          if (quality_set) {
+            fprintf(stderr, "quality already set\n");
+            return COMMAND_INVALID;
+          }
           quality_set = ParseInt(value, BROTLI_MIN_QUALITY,
                                  BROTLI_MAX_QUALITY, &params->quality);
-          if (!quality_set) return COMMAND_INVALID;
+          if (!quality_set) {
+            fprintf(stderr, "error parsing quality value [%s]\n", value);
+            return COMMAND_INVALID;
+          }
         } else if (strncmp("suffix", arg, key_len) == 0) {
-          if (suffix_set) return COMMAND_INVALID;
+          if (suffix_set) {
+            fprintf(stderr, "suffix already set\n");
+            return COMMAND_INVALID;
+          }
           suffix_set = BROTLI_TRUE;
           params->suffix = value;
         } else {
+          fprintf(stderr, "invalid parameter: [%s]\n", arg);
           return COMMAND_INVALID;
         }
       }
diff --git a/docs/encode.h.3 b/docs/encode.h.3
index 906ce07..eff57bd 100644
--- a/docs/encode.h.3
+++ b/docs/encode.h.3
@@ -294,6 +294,16 @@
 .TP
 \fB\fIBROTLI_PARAM_LARGE_WINDOW \fP\fP
 Flag that determines if 'Large Window Brotli' is used\&. 
+.TP
+\fB\fIBROTLI_PARAM_NPOSTFIX \fP\fP
+Recommended number of postfix bits (NPOSTFIX)\&. Encoder may change this value\&.
+.PP
+Range is from 0 to ::BROTLI_MAX_NPOSTFIX\&. 
+.TP
+\fB\fIBROTLI_PARAM_NDIRECT \fP\fP
+Recommended number of direct distance codes (NDIRECT)\&. Encoder may change this value\&.
+.PP
+Range is from 0 to (15 << NPOSTFIX) in steps of (1 << NPOSTFIX)\&. 
 .SH "Function Documentation"
 .PP 
 .SS "\fBBROTLI_BOOL\fP BrotliEncoderCompress (int quality, int lgwin, \fBBrotliEncoderMode\fP mode, size_t input_size, const uint8_t input_buffer[input_size], size_t * encoded_size, uint8_t encoded_buffer[*encoded_size])"
diff --git a/research/durchschlag.cc b/research/durchschlag.cc
index cc4ed68..2fbf41b 100755
--- a/research/durchschlag.cc
+++ b/research/durchschlag.cc
@@ -75,6 +75,8 @@
   return output;
 }
 
+/* precondition: span > 0
+   precondition: end + span == len(shortcut) */
 static Score buildCandidatesList(std::vector<Candidate>* candidates,
     std::vector<MetaSlot>* map, TextIdx span, const TextIdx* shortcut,
     TextIdx end) {
@@ -87,7 +89,10 @@
   }
 
   Score score = 0;
-  for (size_t j = 0; j < span; ++j) {
+  /* Consider the whole span, except one last item. The following loop will
+     add the last item to the end of the "chain", evaluate it, and cut one
+     "link" form the beginning. */
+  for (size_t j = 0; j < span - 1; ++j) {
     MetaSlot& item = slots[shortcut[j]];
     if (item.mark == 0) {
       score += item.score;
@@ -99,7 +104,8 @@
   TextIdx limit = std::min<TextIdx>(end, CANDIDATE_BUNDLE_SIZE);
   Score maxScore = 0;
   for (; i < limit; ++i) {
-    MetaSlot& pick = slots[shortcut[i + span]];
+    TextIdx slice = shortcut[i + span - 1];
+    MetaSlot& pick = slots[slice];
     if (pick.mark == 0) {
       score += pick.score;
     }
@@ -120,7 +126,8 @@
   std::make_heap(candidates->begin(), candidates->end(), greaterScore());
   Score minScore = candidates->at(0).score;
   for (; i < end; ++i) {
-    MetaSlot& pick = slots[shortcut[i + span]];
+    TextIdx slice = shortcut[i + span - 1];
+    MetaSlot& pick = slots[slice];
     if (pick.mark == 0) {
       score += pick.score;
     }
@@ -156,6 +163,8 @@
   return minScore;
 }
 
+/* precondition: span > 0
+   precondition: end + span == len(shortcut) */
 static Score rebuildCandidatesList(std::vector<TextIdx>* candidates,
     std::vector<MetaSlot>* map, TextIdx span, const TextIdx* shortcut,
     TextIdx end, TextIdx* next) {
@@ -172,7 +181,10 @@
   }
 
   Score score = 0;
-  for (TextIdx i = 0; i < span; ++i) {
+  /* Consider the whole span, except one last item. The following loop will
+     add the last item to the end of the "chain", evaluate it, and cut one
+     "link" form the beginning. */
+  for (TextIdx i = 0; i < span - 1; ++i) {
     MetaSlot& item = slots[shortcut[i]];
     if (item.mark == 0) {
       score += item.score;
@@ -182,7 +194,7 @@
 
   Score maxScore = 0;
   for (TextIdx i = 0; i < end; ++i) {
-    MetaSlot& pick = slots[shortcut[i + span]];
+    MetaSlot& pick = slots[shortcut[i + span - 1]];
     if (pick.mark == 0) {
       score += pick.score;
     }
@@ -460,10 +472,10 @@
   }
   TextIdx end = total - sliceLen + 1;
   ScoreSlices(offsets, map, shortcut, end);
-  end = total - blockLen + 1;
+  TextIdx span = blockLen - sliceLen + 1;
+  end = static_cast<TextIdx>(context.sliceMap.size()) - span;
   std::vector<TextIdx> candidates;
   std::vector<TextIdx> next(end);
-  TextIdx span = blockLen - sliceLen + 1;
   Score maxScore = rebuildCandidatesList(
       &candidates, &map, span, shortcut, end, next.data());
 
@@ -499,7 +511,7 @@
       numTries++;
       numCandidates++;
       Score score = 0;
-      for (size_t j = candidate; j <= candidate + span; ++j) {
+      for (size_t j = candidate; j < candidate + span; ++j) {
         MetaSlot& item = map[shortcut[j]];
         if (item.mark != mark) {
           score += item.score;
@@ -522,7 +534,7 @@
         fprintf(stderr, "Broken invariant\n");
         return "";
       }
-      for (TextIdx j = candidate; j <= candidate + span; ++j) {
+      for (TextIdx j = candidate; j < candidate + span; ++j) {
         MetaSlot& item = map[shortcut[j]];
         item.score = 0;
       }
@@ -566,10 +578,10 @@
   }
   TextIdx end = total - sliceLen + 1;
   ScoreSlices(offsets, map, shortcut, end);
-  end = total - blockLen + 1;
+  TextIdx span = blockLen - sliceLen + 1;
+  end = static_cast<TextIdx>(context.sliceMap.size()) - span;
   std::vector<Candidate> candidates;
   candidates.reserve(CANDIDATE_BUNDLE_SIZE + 1024);
-  TextIdx span = blockLen - sliceLen + 1;
   Score minScore = buildCandidatesList(&candidates, &map, span, shortcut, end);
 
   /* Block selection */
@@ -598,7 +610,7 @@
       candidates.pop_back();
       mark++;
       Score score = 0;
-      for (TextIdx j = candidate; j <= candidate + span; ++j) {
+      for (TextIdx j = candidate; j < candidate + span; ++j) {
         MetaSlot& item = map[shortcut[j]];
         if (item.mark != mark) {
           score += item.score;
@@ -614,7 +626,7 @@
       } else if (score > expectedScore) {
         fatal("Broken invariant");
       }
-      for (TextIdx j = candidate; j <= candidate + span; ++j) {
+      for (TextIdx j = candidate; j < candidate + span; ++j) {
         MetaSlot& item = map[shortcut[j]];
         item.score = 0;
       }
diff --git a/scripts/appveyor.yml b/scripts/appveyor.yml
index f5f0c13..c7881ad 100644
--- a/scripts/appveyor.yml
+++ b/scripts/appveyor.yml
@@ -42,7 +42,7 @@
     )
   )
 - IF "%BUILD_SYSTEM%"=="bazel" (
-    appveyor DownloadFile https://github.com/bazelbuild/bazel/releases/download/0.10.0/bazel-0.10.0-windows-x86_64.exe -FileName bazel.exe
+    appveyor DownloadFile https://github.com/bazelbuild/bazel/releases/download/0.11.1/bazel-0.11.1-windows-x86_64.exe -FileName bazel.exe
   )
 
 before_build:
diff --git a/scripts/sources.lst b/scripts/sources.lst
index cdddb37..4ca22bc 100644
--- a/scripts/sources.lst
+++ b/scripts/sources.lst
@@ -81,6 +81,7 @@
   c/enc/memory.h \
   c/enc/metablock.h \
   c/enc/metablock_inc.h \
+  c/enc/params.h \
   c/enc/prefix.h \
   c/enc/quality.h \
   c/enc/ringbuffer.h \
diff --git a/setup.py b/setup.py
index d8478b3..7535fb2 100644
--- a/setup.py
+++ b/setup.py
@@ -249,6 +249,7 @@
             'c/enc/memory.h',
             'c/enc/metablock.h',
             'c/enc/metablock_inc.h',
+            'c/enc/params.h',
             'c/enc/prefix.h',
             'c/enc/quality.h',
             'c/enc/ringbuffer.h',