/* trees.c -- output deflated data using Huffman coding
- * Copyright (C) 1995-2005 Jean-loup Gailly
+ * Copyright (C) 1995-2006 Jean-loup Gailly
+ * detect_data_type() function provided freely by Cosmin Truta, 2006
* For conditions of distribution and use, see copyright notice in zlib.h
*/
int blcodes));
local void compress_block OF((deflate_state *s, ct_data *ltree,
ct_data *dtree));
-local void set_data_type OF((deflate_state *s));
+local int detect_data_type OF((deflate_state *s));
local unsigned bi_reverse OF((unsigned value, int length));
local void bi_windup OF((deflate_state *s));
local void bi_flush OF((deflate_state *s));
if (static_init_done) return;
/* For some embedded targets, global variables are not initialized: */
+#ifdef NO_INIT_GLOBAL_POINTERS
static_l_desc.static_tree = static_ltree;
static_l_desc.extra_bits = extra_lbits;
static_d_desc.static_tree = static_dtree;
static_d_desc.extra_bits = extra_dbits;
static_bl_desc.extra_bits = extra_blbits;
+#endif
/* Initialize the mapping length (0..255) -> length code (0..28) */
length = 0;
if (s->level > 0) {
/* Check if the file is binary or text */
- if (stored_len > 0 && s->strm->data_type == Z_UNKNOWN)
- set_data_type(s);
+ if (s->strm->data_type == Z_UNKNOWN)
+ s->strm->data_type = detect_data_type(s);
/* Construct the literal and distance trees */
build_tree(s, (tree_desc *)(&(s->l_desc)));
}
/* ===========================================================================
- * Set the data type to BINARY or TEXT, using a crude approximation:
- * set it to Z_TEXT if all symbols are either printable characters (33 to 255)
- * or white spaces (9 to 13, or 32); or set it to Z_BINARY otherwise.
+ * Check if the data type is TEXT or BINARY, using the following algorithm:
+ * - TEXT if the two conditions below are satisfied:
+ * a) There are no non-portable control characters belonging to the
+ * "black list" (0..6, 14..25, 28..31).
+ * b) There is at least one printable character belonging to the
+ * "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
+ * - BINARY otherwise.
+ * - The following partially-portable control characters form a
+ * "gray list" that is ignored in this detection algorithm:
+ * (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
* IN assertion: the fields Freq of dyn_ltree are set.
*/
-local void set_data_type(s)
+local int detect_data_type(s)
deflate_state *s;
{
+ /* black_mask is the bit mask of black-listed bytes
+ * set bits 0..6, 14..25, and 28..31
+ * 0xf3ffc07f = binary 11110011111111111100000001111111
+ */
+ unsigned long black_mask = 0xf3ffc07fUL;
int n;
- for (n = 0; n < 9; n++)
+ /* Check for non-textual ("black-listed") bytes. */
+ for (n = 0; n <= 31; n++, black_mask >>= 1)
+ if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
+ return Z_BINARY;
+
+ /* Check for textual ("white-listed") bytes. */
+ if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
+ || s->dyn_ltree[13].Freq != 0)
+ return Z_TEXT;
+ for (n = 32; n < LITERALS; n++)
if (s->dyn_ltree[n].Freq != 0)
- break;
- if (n == 9)
- for (n = 14; n < 32; n++)
- if (s->dyn_ltree[n].Freq != 0)
- break;
- s->strm->data_type = (n == 32) ? Z_TEXT : Z_BINARY;
+ return Z_TEXT;
+
+ /* There are no "black-listed" or "white-listed" bytes:
+ * this stream either is empty or has tolerated ("gray-listed") bytes only.
+ */
+ return Z_BINARY;
}
/* ===========================================================================