This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision | ||
|
api:buffer [2016/06/18 20:49] payonel [Instance Methods] |
api:buffer [2016/06/19 07:56] (current) payonel [Instance Methods] |
||
|---|---|---|---|
| Line 47: | Line 47: | ||
| - `b:lines([line_formats...]) string array` | - `b:lines([line_formats...]) string array` | ||
| - | Returns a function iterator which reads from the stream until it reaches nil. On each read, the `line_formats` list of args ais passed to `stream:read(...)`. The overwhelmingly typical use is to not define `line_formats`, i.e. passing no args to `lines()`. The default behavior (i..e without `line_formats`) is to read a "line" at a time from the stream. | + | Returns a function iterator which reads from the stream until it reaches nil. On each read, the `line_formats` list of args as passed to `stream:read(...)`. The overwhelmingly typical use is to not define `line_formats`, i.e. passing no args to `lines()`. The default behavior (i..e without `line_formats`) is to read a "line" at a time from the stream. |
| ```lua | ```lua | ||
| Line 62: | Line 62: | ||
| | | ||
| Each `format` is read from the stream and all returned in a multiple return value list of the results. Note all format strings are prefixed with \* and also note that only the first char of the string names of the formats matters, the rest is ignored. These are the supported formats: | Each `format` is read from the stream and all returned in a multiple return value list of the results. Note all format strings are prefixed with \* and also note that only the first char of the string names of the formats matters, the rest is ignored. These are the supported formats: | ||
| - | ``` | + | |
| - | local file = io.open( | + | * a number value, e.g. `10` |
| - | ``` | + | |
| - | * a number value, e.g. `b:read(10)` | + | Read **n** bytes (in binary mode) or chars (in text mode) from the stream; result is returned as a string. See [[api:non-standard-lua-libs#input_and_output_facilities|io.open]] for more details about how to open files in different modes. |
| - | Read **n** bytes from the stream, result is a string | + | |
| - | + | `local chars = b:read(10)` | |
| - | * "\*n", "\*number" | + | |
| - | Read the next series of bytes from the stream and that can be interpreted as a number | + | * "\*n" or "\*number" |
| - | + | ||
| - | * "\*l", "\*line" | + | Read the next series of bytes from the stream that can be interpreted as a number. Note that reading numbers is also affected by the open mode, binary or text. See [[api:non-standard-lua-libs#input_and_output_facilities|io.open]] for more details about how to open files in different modes.. |
| - | Read the next line from the stream, chopping off the line ending marker (which may be \n, \r, or \r\n) | + | |
| - | + | `local number = b:read("*n")` | |
| - | * "\*L", "\*Line" | + | |
| - | Read the next line from the stream, like "*line", but preserves the line ending marker as part of the result | + | * "\*l" or "\*line" |
| - | + | ||
| - | * "\*a", "\*all" | + | Read the next line from the stream, chopping off the line ending marker (which may be \n, \r, or \r\n) |
| - | Reads all remaining data from the stream until nil. There would be no point in having formats following this. | + | |
| + | `local line = b:read("*l")` | ||
| + | |||
| + | * "\*L" or "\*Line" | ||
| + | |||
| + | Read the next line from the stream, like "*line", but preserves the line ending marker as part of the result | ||
| + | |||
| + | `local whole_line = b:read("*L")` | ||
| + | |||
| + | * "\*a" or "\*all" | ||
| + | |||
| + | Reads all remaining data from the stream until nil. There would be no point in having formats following this. | ||
| + | |||
| + | `local the_whole_file = b:read("*a")` | ||
| - `b:getTimeout() number` | - `b:getTimeout() number` | ||
| Line 86: | Line 99: | ||
| Sets the time in seconds a buffered stream will try to limit a `read` operation. Note that this timeout cannot be strictly adhered to. A read operation that completes within a single `readChunk` (an internal method that invokes the actual `read` on the stream) does not check the `timeout` limit. Timeout is only checked between stream reads within a single buffered read (an example follows). Thus, if a read requires multiple chunk reads, and the time between the start of the first read before the start of the last read is greater than or equal to the timeout, then the buffered stream will error. Again note that a timeout is default `math.huge`. | Sets the time in seconds a buffered stream will try to limit a `read` operation. Note that this timeout cannot be strictly adhered to. A read operation that completes within a single `readChunk` (an internal method that invokes the actual `read` on the stream) does not check the `timeout` limit. Timeout is only checked between stream reads within a single buffered read (an example follows). Thus, if a read requires multiple chunk reads, and the time between the start of the first read before the start of the last read is greater than or equal to the timeout, then the buffered stream will error. Again note that a timeout is default `math.huge`. | ||
| - | | + | |
| ```lua | ```lua | ||
| - | local file = buffer.new("r", { read = function() os.sleep(5) return "abc" end }) | + | local file = buffer.new("r", { read = function() os.sleep(5) return "a" end }) |
| file:setvbuf("full", 1) -- set buffer size to 1 char | file:setvbuf("full", 1) -- set buffer size to 1 char | ||
| file:setTimeout(1) -- set buffer timeout to 1 second | file:setTimeout(1) -- set buffer timeout to 1 second | ||
| Line 94: | Line 108: | ||
| local a, b = file:read(1, 1) -- read 1 char, then read 1 char again | local a, b = file:read(1, 1) -- read 1 char, then read 1 char again | ||
| ``` | ``` | ||
| - | | ||
| - | - `b:seek` | ||
| - | about seek | + | - `b:seek([whence:string], [offset:number])` |
| + | |||
| + | Moves the stream position by `offset` bytes from `whence`, both optional params. `whence` defaults to "cur", and `offset` defaults to 0. | ||
| + | Valid `whence` values: | ||
| + | - "cur" from the current position. | ||
| + | - "set" from the start of the stream. | ||
| + | - "end" from the end of the stream. | ||
| + | Returns the result of the seek operation on the stream (which may fail). | ||
| Interface Methods | Interface Methods | ||
| ----------- | ----------- | ||
| + | |||
| The following methods are expected to be implemented on the buffered streams passed to `buffer.new`. | The following methods are expected to be implemented on the buffered streams passed to `buffer.new`. | ||
| - | close | + | - `close() ok, reason` |
| - | write | + | |
| - | read | + | Close handles, release resources, disconnect -- and return success |
| - | seek | + | |
| + | - `write(arg: string) ok, reason` | ||
| + | |||
| + | Write `arg` as bytes, assume a string of plain unformatted chars. Return falsey and reason on failure. | ||
| + | |||
| + | - `read(n: number) ok, reason` | ||
| + | |||
| + | Return `n` bytes, and **not** `n` unicode-aware chars. Assume your data is binary data and let the buffer library manage the mode and the unicode string packaging (if applicable). Note that this is exactly how the [[api:filesystem|filesystem]] library operates.The caller assumes there is more data to read until `nil` is returned. A empty string or a string shorter than `n` chars long is a valid return, but the caller may assume there is more data to request until `nil` is returned. | ||
| + | |||
| + | - `seek([whence: string], [offset: number]) [offset from start] or falsey, reason` | ||
| + | |||
| + | Refer to `b:seek()` for details. In short, move the stream position to `offset` from `whence`, and return the `offset` from the start of the stream of the position after the seek operation. Note that `seek("cur", 0)` is a valid request, typical of the caller wanting to determine the current position of the stream. Your stream is not required to support `seek`, in such case (or in any case of failure) you should return nil, and the reason (as a string) for the failure. | ||