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diff --git a/chromium/third_party/sqlite/sqlite-src-3240000/ext/icu/README.txt b/chromium/third_party/sqlite/sqlite-src-3240000/ext/icu/README.txt deleted file mode 100644 index af75d22e611..00000000000 --- a/chromium/third_party/sqlite/sqlite-src-3240000/ext/icu/README.txt +++ /dev/null @@ -1,169 +0,0 @@ - -This directory contains source code for the SQLite "ICU" extension, an -integration of the "International Components for Unicode" library with -SQLite. Documentation follows. - - 1. Features - - 1.1 SQL Scalars upper() and lower() - 1.2 Unicode Aware LIKE Operator - 1.3 ICU Collation Sequences - 1.4 SQL REGEXP Operator - - 2. Compilation and Usage - - 3. Bugs, Problems and Security Issues - - 3.1 The "case_sensitive_like" Pragma - 3.2 The SQLITE_MAX_LIKE_PATTERN_LENGTH Macro - 3.3 Collation Sequence Security Issue - - -1. FEATURES - - 1.1 SQL Scalars upper() and lower() - - SQLite's built-in implementations of these two functions only - provide case mapping for the 26 letters used in the English - language. The ICU based functions provided by this extension - provide case mapping, where defined, for the full range of - unicode characters. - - ICU provides two types of case mapping, "general" case mapping and - "language specific". Refer to ICU documentation for the differences - between the two. Specifically: - - http://www.icu-project.org/userguide/caseMappings.html - http://www.icu-project.org/userguide/posix.html#case_mappings - - To utilise "general" case mapping, the upper() or lower() scalar - functions are invoked with one argument: - - upper('abc') -> 'ABC' - lower('ABC') -> 'abc' - - To access ICU "language specific" case mapping, upper() or lower() - should be invoked with two arguments. The second argument is the name - of the locale to use. Passing an empty string ("") or SQL NULL value - as the second argument is the same as invoking the 1 argument version - of upper() or lower(): - - lower('I', 'en_us') -> 'i' - lower('I', 'tr_tr') -> 'ı' (small dotless i) - - 1.2 Unicode Aware LIKE Operator - - Similarly to the upper() and lower() functions, the built-in SQLite LIKE - operator understands case equivalence for the 26 letters of the English - language alphabet. The implementation of LIKE included in this - extension uses the ICU function u_foldCase() to provide case - independent comparisons for the full range of unicode characters. - - The U_FOLD_CASE_DEFAULT flag is passed to u_foldCase(), meaning the - dotless 'I' character used in the Turkish language is considered - to be in the same equivalence class as the dotted 'I' character - used by many languages (including English). - - 1.3 ICU Collation Sequences - - A special SQL scalar function, icu_load_collation() is provided that - may be used to register ICU collation sequences with SQLite. It - is always called with exactly two arguments, the ICU locale - identifying the collation sequence to ICU, and the name of the - SQLite collation sequence to create. For example, to create an - SQLite collation sequence named "turkish" using Turkish language - sorting rules, the SQL statement: - - SELECT icu_load_collation('tr_TR', 'turkish'); - - Or, for Australian English: - - SELECT icu_load_collation('en_AU', 'australian'); - - The identifiers "turkish" and "australian" may then be used - as collation sequence identifiers in SQL statements: - - CREATE TABLE aust_turkish_penpals( - australian_penpal_name TEXT COLLATE australian, - turkish_penpal_name TEXT COLLATE turkish - ); - - 1.4 SQL REGEXP Operator - - This extension provides an implementation of the SQL binary - comparision operator "REGEXP", based on the regular expression functions - provided by the ICU library. The syntax of the operator is as described - in SQLite documentation: - - <string> REGEXP <re-pattern> - - This extension uses the ICU defaults for regular expression matching - behavior. Specifically, this means that: - - * Matching is case-sensitive, - * Regular expression comments are not allowed within patterns, and - * The '^' and '$' characters match the beginning and end of the - <string> argument, not the beginning and end of lines within - the <string> argument. - - Even more specifically, the value passed to the "flags" parameter - of ICU C function uregex_open() is 0. - - -2 COMPILATION AND USAGE - - The easiest way to compile and use the ICU extension is to build - and use it as a dynamically loadable SQLite extension. To do this - using gcc on *nix: - - gcc -shared icu.c `icu-config --ldflags` -o libSqliteIcu.so - - You may need to add "-I" flags so that gcc can find sqlite3ext.h - and sqlite3.h. The resulting shared lib, libSqliteIcu.so, may be - loaded into sqlite in the same way as any other dynamically loadable - extension. - - -3 BUGS, PROBLEMS AND SECURITY ISSUES - - 3.1 The "case_sensitive_like" Pragma - - This extension does not work well with the "case_sensitive_like" - pragma. If this pragma is used before the ICU extension is loaded, - then the pragma has no effect. If the pragma is used after the ICU - extension is loaded, then SQLite ignores the ICU implementation and - always uses the built-in LIKE operator. - - The ICU extension LIKE operator is always case insensitive. - - 3.2 The SQLITE_MAX_LIKE_PATTERN_LENGTH Macro - - Passing very long patterns to the built-in SQLite LIKE operator can - cause excessive CPU usage. To curb this problem, SQLite defines the - SQLITE_MAX_LIKE_PATTERN_LENGTH macro as the maximum length of a - pattern in bytes (irrespective of encoding). The default value is - defined in internal header file "limits.h". - - The ICU extension LIKE implementation suffers from the same - problem and uses the same solution. However, since the ICU extension - code does not include the SQLite file "limits.h", modifying - the default value therein does not affect the ICU extension. - The default value of SQLITE_MAX_LIKE_PATTERN_LENGTH used by - the ICU extension LIKE operator is 50000, defined in source - file "icu.c". - - 3.3 Collation Sequence Security Issue - - Internally, SQLite assumes that indices stored in database files - are sorted according to the collation sequence indicated by the - SQL schema. Changing the definition of a collation sequence after - an index has been built is therefore equivalent to database - corruption. The SQLite library is not very well tested under - these conditions, and may contain potential buffer overruns - or other programming errors that could be exploited by a malicious - programmer. - - If the ICU extension is used in an environment where potentially - malicious users may execute arbitrary SQL (i.e. gears), they - should be prevented from invoking the icu_load_collation() function, - possibly using the authorisation callback. |