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Replace black/white with allow/block. (theresa-m)

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This commit is contained in:
Mark Adler 2021-12-31 16:57:07 -08:00
parent c3f3043f7a
commit 8678871f18
2 changed files with 15 additions and 15 deletions
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12
doc/txtvsbin.txt
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@ -38,15 +38,15 @@ The Algorithm
The algorithm works by dividing the set of bytecodes [0..255] into three
categories:
- The white list of textual bytecodes:
- The allow list of textual bytecodes:
9 (TAB), 10 (LF), 13 (CR), 32 (SPACE) to 255.
- The gray list of tolerated bytecodes:
7 (BEL), 8 (BS), 11 (VT), 12 (FF), 26 (SUB), 27 (ESC).
- The black list of undesired, non-textual bytecodes:
- The block list of undesired, non-textual bytecodes:
0 (NUL) to 6, 14 to 31.
If a file contains at least one byte that belongs to the white list and
no byte that belongs to the black list, then the file is categorized as
If a file contains at least one byte that belongs to the allow list and
no byte that belongs to the block list, then the file is categorized as
plain text; otherwise, it is categorized as binary. (The boundary case,
when the file is empty, automatically falls into the latter category.)
@ -84,9 +84,9 @@ consistent results, regardless what alphabet encoding is being used.
results on a text encoded, say, using ISO-8859-16 versus UTF-8.)
There is an extra category of plain text files that are "polluted" with
one or more black-listed codes, either by mistake or by peculiar design
one or more block-listed codes, either by mistake or by peculiar design
considerations. In such cases, a scheme that tolerates a small fraction
of black-listed codes would provide an increased recall (i.e. more true
of block-listed codes would provide an increased recall (i.e. more true
positives). This, however, incurs a reduced precision overall, since
false positives are more likely to appear in binary files that contain
large chunks of textual data. Furthermore, "polluted" plain text should

18
trees.c
View File

@ -1091,9 +1091,9 @@ local void compress_block(s, ltree, dtree)
* 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).
* "block 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).
* "allow 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:
@ -1103,19 +1103,19 @@ local void compress_block(s, ltree, dtree)
local int detect_data_type(s)
deflate_state *s;
{
/* black_mask is the bit mask of black-listed bytes
/* block_mask is the bit mask of block-listed bytes
* set bits 0..6, 14..25, and 28..31
* 0xf3ffc07f = binary 11110011111111111100000001111111
*/
unsigned long black_mask = 0xf3ffc07fUL;
unsigned long block_mask = 0xf3ffc07fUL;
int 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))
/* Check for non-textual ("block-listed") bytes. */
for (n = 0; n <= 31; n++, block_mask >>= 1)
if ((block_mask & 1) && (s->dyn_ltree[n].Freq != 0))
return Z_BINARY;
/* Check for textual ("white-listed") bytes. */
/* Check for textual ("allow-listed") bytes. */
if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
|| s->dyn_ltree[13].Freq != 0)
return Z_TEXT;
@ -1123,7 +1123,7 @@ local int detect_data_type(s)
if (s->dyn_ltree[n].Freq != 0)
return Z_TEXT;
/* There are no "black-listed" or "white-listed" bytes:
/* There are no "block-listed" or "allow-listed" bytes:
* this stream either is empty or has tolerated ("gray-listed") bytes only.
*/
return Z_BINARY;