US-ASCII string support.
The following functions act only on US-ASCII code points, that is on the bytes in range [0x00;0x7F]. The functions can be safely used on UTF-8 encoded strings but they will, of course, only deal with US-ASCII related matters.
References.
is_valid s is true iff only for all indices i of s, s.[i] is an US-ASCII character, i.e. a byte in the range [0x00;0x1F].
The functions can be safely used on UTF-8 encoded strings; they will of course only deal with US-ASCII casings.
uppercase s is s with US-ASCII characters 'a' to 'z' mapped to 'A' to 'Z'.
lowercase s is s with US-ASCII characters 'A' to 'Z' mapped to 'a' to 'z'.
capitalize s is like uppercase but performs the map only on s.[0].
uncapitalize s is like lowercase but performs the map only on s.[0].
to_hex s is the sequence of bytes of s as US-ASCII lowercase hexadecimal digits.
val of_hex : string -> (string, int) resultof_hex h parses a sequence of US-ASCII (lower or upper cased) hexadecimal digits from h into its corresponding byte sequence. Error n is returned either with n an index in the string which is not a hexadecimal digit or the length of h if it there is a missing digit at the end.
escape s escapes bytes of s to a representation that uses only US-ASCII printable characters. More precisely:
0x20;0x5B] and [0x5D;0x7E] are left unchanged. These are the printable US-ASCII bytes, except '\\' (0x5C).0x00;0x1F], 0x5C and [0x7F;0xFF] are escaped by an hexadecimal "\xHH" escape with H a capital hexadecimal number. These bytes are the US-ASCII control characters, the non US-ASCII bytes and '\\' (0x5C).Use unescape to unescape. The invariant unescape (escape s) = Ok s holds.
val unescape : string -> (string, int) resultunescape s unescapes from s the escapes performed by escape. More precisely:
"\xHH" with H a lower or upper case hexadecimal number is unescaped to the corresponding byte value.Any other escape following a '\\' not defined above makes the function return Error i with i the index of the error in the string.
ocaml_string_escape s escapes the bytes of s to a representation that uses only US-ASCII printable characters and according to OCaml's conventions for string literals. More precisely:
'\b' (0x08) is escaped to "\\b" (0x5C,0x62).'\t' (0x09) is escaped to "\\t" (0x5C,0x74).'\n' (0x0A) is escaped to "\\n" (0x5C,0x6E).'\r' (0x0D) is escaped to "\\r" (0x5C,0x72).'\"' (0x22) is escaped to "\\\"" (0x5C,0x22).'\\' (0x5C) is escaped to "\\\\" (0x5C,0x5C).0x20, 0x21, [0x23;0x5B] and [0x5D;0x7E] are left unchanged. These are the printable US-ASCII bytes, except '\"' (0x22) and '\\' (0x5C)."\xHH" escape with H an uppercase hexadecimal number. These bytes are the US-ASCII control characters not mentioned above and non US-ASCII bytes.Use ocaml_unescape to unescape. The invariant ocaml_unescape (ocaml_string_escape s) = Ok s holds.
val ocaml_unescape : string -> (string, int) resultocaml_unescape s unescapes from s the escape sequences afforded by OCaml string and char literals. More precisely:
"\\b" (0x5C,0x62) is unescaped to '\b' (0x08)."\\t" (0x5C,0x74) is unescaped to '\t' (0x09)."\\n" (0x5C,0x6E) is unescaped to '\n' (0x0A)."\\r" (0x5C,0x72) is unescaped to '\r' (0x0D)."\\ " (0x5C,0x20) is unescaped to ' ' (0x20)."\\\"" (0x5C,0x22) is unescaped to '\"' (0x22)."\\'" (0x5C,0x27) is unescaped to '\'' (0x27)."\\\\" (0x5C,0x5C) is unescaped to '\\' (0x5C)."\xHH" with H a lower or upper case hexadecimal number is unescaped to the corresponding byte value."\\DDD" with D a decimal number such that DDD is unescaped to the corresponding byte value."\\oOOO" with O an octal number is unescaped to the corresponding byte value.Any other escape following a '\\' not defined above makes the function return Error i with i the location of the error in the string.