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Baseline version of Pipe library (#2797)

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Terry Ellison 2019-06-19 15:16:17 +03:00 committed by GitHub
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1
app/include/user_modules.h
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@ -42,6 +42,7 @@
#define LUA_USE_MODULES_OW #define LUA_USE_MODULES_OW
//#define LUA_USE_MODULES_PCM //#define LUA_USE_MODULES_PCM
//#define LUA_USE_MODULES_PERF //#define LUA_USE_MODULES_PERF
//#define LUA_USE_MODULES_PIPE
//#define LUA_USE_MODULES_PWM //#define LUA_USE_MODULES_PWM
//#define LUA_USE_MODULES_PWM2 //#define LUA_USE_MODULES_PWM2
//#define LUA_USE_MODULES_RC //#define LUA_USE_MODULES_RC

309
app/modules/pipe.c Normal file
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/*
** The pipe algo is somewhat similar to the luaL_Buffer algo, except that it uses
** table to store the LUAL_BUFFERSIZE byte array chunks instead of the stack.
** Writing is always to the last UD in the table and overflow pushes a new UD to
** the end of the table. Reading is always from the first UD in the table and
** underrun removes the first UD to shift a new one into slot 1.
**
** Reads and writes may span multiple UD buffers and if the read spans multiple UDs
** then the parts are collected as strings on the Lua stack and then concatenated
** with a `lua_concat()`.
**
** Note that pipes also support the undocumented length and tostring operators
** for debugging puposes, so if p is a pipe then #p[1] gives the effective
** length of pipe slot 1 and printing p[1] gives its contents
**
** Read the docs/modules/pipe.md documentation for a functional description.
*/
#include "module.h"
#include "lauxlib.h"
#include <string.h>
#define INVALID_LEN ((unsigned)-1)
#define LUA_USE_MODULES_PIPE
typedef struct buffer {
int start, end;
char buf[LUAL_BUFFERSIZE];
} buffer_t;
LROT_TABLE(pipe_meta)
/* Validation and utility functions */
#define AT_HEAD 1
#define AT_TAIL 0
static buffer_t *checkPipeUD (lua_State *L, int ndx) { // [-0, +0, v]
buffer_t *ud = lua_touserdata(L, ndx);
if (ud && lua_getmetatable(L, ndx)) { /* Get UD and its metatable? */
lua_pushrotable(L, LROT_TABLEREF(pipe_meta)); /* push correct metatable */
if (lua_rawequal(L, -1, -2)) { /* Do these match? */
lua_pop(L, 2); /* remove both metatables */
return ud; /* and return ptr to buffer_t rec */
}
}
if (!lua_istable(L,ndx))
luaL_typerror(L, ndx, "pipeUD"); /* NORETURN error */
return NULL; /* keep compiler happy */
}
static buffer_t *newPipeUD(lua_State *L, int ndx, int n) { // [-0,+0,-]
buffer_t *ud = (buffer_t *) lua_newuserdata(L, sizeof(buffer_t));
lua_pushrotable(L, LROT_TABLEREF(pipe_meta)); /* push the metatable */
lua_setmetatable(L, -2); /* set UD's metabtable to pipe_meta */
ud->start = ud->end = 0;
lua_rawseti(L, ndx, n); /* T[#T+1] = new UD */
return ud; /* ud points to new T[#T] */
}
static buffer_t *checkPipeTable (lua_State *L, int tbl, int head) {//[-0, +0, v]
int m = lua_gettop(L), n = lua_objlen(L, tbl);
if (lua_type(L, tbl) == LUA_TTABLE && lua_getmetatable(L, tbl)) {
lua_pushrotable(L, LROT_TABLEREF(pipe_meta));/* push comparison metatable */
if (lua_rawequal(L, -1, -2)) { /* check these match */
buffer_t *ud;
if (n == 0) {
ud = head ? NULL : newPipeUD(L, tbl, 1);
} else {
int i = head ? 1 : n; /* point to head or tail of T */
lua_rawgeti(L, tbl, i); /* and fetch UD */
ud = checkPipeUD(L, -1);
}
lua_settop(L, m);
return ud; /* and return ptr to buffer_t rec */
}
}
luaL_typerror(L, tbl, "pipe table");
return NULL; /* NORETURN avoid compiler error */
}
#define CHAR_DELIM -1
#define CHAR_DELIM_KEEP -2
static char getsize_delim (lua_State *L, int ndx, int *len) { // [-0, +0, v]
char delim;
int n;
if( lua_type( L, ndx ) == LUA_TNUMBER ) {
n = luaL_checkinteger( L, ndx );
luaL_argcheck(L, n > 0, ndx, "invalid chunk size");
delim = '\0';
} else if (lua_isnil(L, ndx)) {
n = CHAR_DELIM;
delim = '\n';
} else {
size_t ldelim;
const char *s = lua_tolstring( L, 2, &ldelim);
n = ldelim == 2 && s[1] == '+' ? CHAR_DELIM_KEEP : CHAR_DELIM ;
luaL_argcheck(L, ldelim + n == 0, ndx, "invalid delimiter");
delim = s[0];
}
if (len)
*len = n;
return delim;
}
/* Lua callable methods */
//Lua s = pipeUD:tostring()
static int pipe__tostring (lua_State *L) {
if (lua_type(L, 1) == LUA_TTABLE) {
lua_pushfstring(L, "Pipe: %p", lua_topointer(L, 1));
} else {
buffer_t *ud = checkPipeUD(L, 1);
lua_pushlstring(L, ud->buf + ud->start, ud->end - ud->start);
}
return 1;
}
// len = #pipeobj[1]
static int pipe__len (lua_State *L) {
if (lua_type(L, 1) == LUA_TTABLE) {
lua_pushinteger(L, lua_objlen(L, 1));
} else {
buffer_t *ud = checkPipeUD(L, 1);
lua_pushinteger(L, ud->end - ud->start);
}
return 1;
}
// Lua: buf = pipe.create()
static int pipe_create(lua_State *L) {
lua_createtable (L, 1, 0);
lua_pushrotable(L, LROT_TABLEREF(pipe_meta));
lua_setmetatable(L, 1); /* set table's metabtable to pipe_meta */
return 1; /* return the table */
}
// Lua: rec = p:read(end_or_delim) // also [-2, +1,- ]
static int pipe_read(lua_State *L) {
buffer_t *ud = checkPipeTable(L, 1, AT_HEAD);
int i, k=0, n;
lua_settop(L,2);
const char delim = getsize_delim(L, 2, &n);
lua_pop(L,1);
while (ud && n) {
int want, used, avail = ud->end - ud->start;
if (n < 0 /* one of the CHAR_DELIM flags */) {
/* getting a delimited chunk so scan for delimiter */
for (i = ud->start; i < ud->end && ud->buf[i] != delim; i++) {}
/* Can't have i = ud->end and ud->buf[i] == delim so either */
/* we've scanned full buffer avail OR we've hit a delim char */
if (i == ud->end) {
want = used = avail; /* case where we've scanned without a hit */
} else {
want = used = i + 1 - ud->start; /* case where we've hit a delim */
if (n == CHAR_DELIM)
want--;
}
} else {
want = used = (n < avail) ? n : avail;
n -= used;
}
lua_pushlstring(L, ud->buf + ud->start, want); /* part we want */
k++;
ud->start += used;
if (ud->start == ud->end) {
/* shift the pipe array down overwriting T[1] */
int nUD = lua_objlen(L, 1);
for (i = 1; i < nUD; i++) { /* for i = 1, nUD-1 */
lua_rawgeti(L, 1, i+1); lua_rawseti(L, 1, i); /* T[i] = T[i+1] */
}
lua_pushnil(L); lua_rawseti(L, 1, nUD--); /* T[n] = nil */
if (nUD) {
lua_rawgeti(L, 1, 1);
ud = checkPipeUD(L, -1);
lua_pop(L, 1);
} else {
ud = NULL;
}
}
}
if (k)
lua_concat(L, k);
else
lua_pushnil(L);
return 1;
}
// Lua: buf:unread(some_string)
static int pipe_unread(lua_State *L) {
size_t l = INVALID_LEN;
const char *s = lua_tolstring(L, 2, &l);
if (l==0)
return 0;
luaL_argcheck(L, l != INVALID_LEN, 2, "must be a string");
buffer_t *ud = checkPipeTable(L, 1, AT_HEAD);
do {
int used = ud->end - ud->start, lrem = LUAL_BUFFERSIZE-used;
if (used == LUAL_BUFFERSIZE) {
int i, nUD = lua_objlen(L, 1);
for (i = nUD; i > 0; i--) { /* for i = nUD-1,1,-1 */
lua_rawgeti(L, 1, i); lua_rawseti(L, 1, i+1); /* T[i+1] = T[i] */
}
ud = newPipeUD(L, 1, 1);
used = 0; lrem = LUAL_BUFFERSIZE;
} else if (ud->end < LUAL_BUFFERSIZE) {
memmove(ud->buf + lrem,
ud->buf + ud->start, used); /* must be memmove not cpy */
}
ud->start = lrem; ud->end = LUAL_BUFFERSIZE;
if (l <= (unsigned )lrem)
break;
/* If we've got here then the remaining string is strictly longer than the */
/* remaining buffer space, so top off the buffer before looping around again */
l -= lrem;
memcpy(ud->buf, s + l, lrem);
ud->start = 0;
} while(1);
/* Copy any residual tail to the UD buffer. Note that this is l>0 and */
ud->start -= l;
memcpy(ud->buf + ud->start, s, l);
return 0;
}
// Lua: buf:write(some_string)
static int pipe_write(lua_State *L) {
size_t l = INVALID_LEN;
const char *s = lua_tolstring(L, 2, &l);
if (l==0)
return 0;
luaL_argcheck(L, l != INVALID_LEN, 2, "must be a string");
buffer_t *ud = checkPipeTable(L, 1, AT_TAIL);
do {
int used = ud->end - ud->start;
if (used == LUAL_BUFFERSIZE) {
ud = newPipeUD(L, 1, lua_objlen(L, 1)+1);
used = 0;
} else if (ud->start) {
memmove(ud->buf, ud->buf + ud->start, used); /* must be memmove not cpy */
ud->start = 0; ud->end = used;
}
int lrem = LUAL_BUFFERSIZE-used;
if (l <= (unsigned )lrem)
break;
/* If we've got here then the remaining string is longer than the buffer */
/* space left, so top off the buffer before looping around again */
memcpy(ud->buf + ud->end, s, lrem);
ud->end += lrem;
l -= lrem;
s += lrem;
} while(1);
/* Copy any residual tail to the UD buffer. Note that this is l>0 and */
memcpy(ud->buf + ud->end, s, l);
ud->end += l;
return 0;
}
// Lua: fread = pobj:reader(1400) -- or other number
// fread = pobj:reader('\n') -- or other delimiter (delim is stripped)
// fread = pobj:reader('\n+') -- or other delimiter (delim is retained)
#define TBL lua_upvalueindex(1)
#define N lua_upvalueindex(2)
static int pipe_read_aux(lua_State *L) {
lua_settop(L, 0); /* ignore args since we use upvals instead */
lua_pushvalue(L, TBL);
lua_pushvalue(L, N);
return pipe_read(L);
}
static int pipe_reader(lua_State *L) {
lua_settop(L,2);
checkPipeTable (L, 1,AT_HEAD);
getsize_delim(L, 2, NULL);
lua_pushcclosure(L, pipe_read_aux, 2); /* return (closure, nil, table) */
return 1;
}
LROT_BEGIN(pipe_meta)
LROT_TABENTRY( __index, pipe_meta)
LROT_FUNCENTRY( __len, pipe__len )
LROT_FUNCENTRY( __tostring, pipe__tostring )
LROT_FUNCENTRY( read, pipe_read )
LROT_FUNCENTRY( reader, pipe_reader )
LROT_FUNCENTRY( unread, pipe_unread )
LROT_FUNCENTRY( write, pipe_write )
LROT_END( pipe_meta, NULL, LROT_MASK_INDEX )
LROT_BEGIN(pipe)
LROT_FUNCENTRY( create, pipe_create )
LROT_END( lb, NULL, 0 )
NODEMCU_MODULE(PIPE, "pipe", pipe, NULL);

131
docs/modules/pipe.md Normal file
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# pipe Module
| Since | Origin / Contributor | Maintainer | Source |
| :----- | :-------------------- | :---------- | :------ |
| 2019-07-18 | [Terry Ellison](https://github.com/TerryE) | [Terry Ellison](https://github.com/TerryE) | [pipe.c](../../app/modules/pipe.c)|
The pipe module provides RAM-efficient a means of passing character stream of records from one Lua
task to another.
## pipe.create()
Create a pipe.
#### Syntax
`pobj = pipe.create()`
#### Parameters
None
#### Returns
A pipe resource.
## pobj:read()
Read a record from a pipe object.
Note that the recommended method of reading from a pipe is to user a reader function as described below.
#### Syntax
`pobj:read([size/end_char])`
#### Parameters
- `size/end_char`
- If numeric then a string of `size` length will be returned from the pipe.
- If a string then this is a single character delimiter, followed by an optional "+" flag. The delimiter is used as an end-of-record to split the character stream into separate records. If the flag "+" is specified then the delimiter is also returned at the end of the record, otherwise it is discarded.
- If omitted, then this defaults to `"\n+"`
Note that if the last record in the pipe is missing a delimiter or is too short, then it is still returned, emptying the pipe.
#### Returns
A string or `nil` if the pipe is empty
#### Example
```lua
line = pobj:read('\n')
line = pobj:read(50)
```
## pobj:reader()
Returns a Lua **iterator** function for a pipe object. This is as described in the
[Lua Language: For Statement](http://www.lua.org/manual/5.1/manual.html#2.4.5). \(Note that the
`state` and `object` variables mentioned in 2.5.4 are optional and default to `nil`, so this
conforms to to the`for` iterator syntax and works in a for because it maintains the state and `pobj`
internally as upvalues.
An emptied pipe takes up minimal RAM resources (an empty Lua array), and just like any other array
this is reclaimed if all variables referencing it go out of scope or are over-written). Note
that any reader iterators that you have created also refer to the pipe as an upval, so you will
need to descard these to desope the pipe array.
#### Syntax
`myFunc = pobj:reader([size/end_char])`
#### Parameters
- `size/end_char` as for `pobj:read()`
#### Returns
- `myFunc` iterator function
#### Examples
- used in `for` loop:
```lua
for rec in p:reader() do print(rec) end
-- or
fp = p:reader()
-- ...
for rec in fp do print(rec) end
```
- used in callback task:
```Lua
do
local pipe_reader = p:reader(1400)
local function flush(sk) -- Upvals flush, pipe_reader
local next = pipe_reader()
if next then
sk:send(next, flush)
else
sk:on('sent') -- dereference to allow GC
flush = nil
end
end
flush()
end
```
## pobj:unread()
Write a string to a head of pipe object. This can be used to back-out a previous read.
#### Syntax
`pobj:write(s)`
#### Parameters
`s` Any input string. Note that with all Lua strings, these may contain all character values including "\0".
#### Returns
Nothing
#### Example
```Lua
a=p:read()
p:unread() -- restores pipe to state before the read
```
## pobj:write()
Write a string to a pipe object.
#### Syntax
`pobj:write(s)`
#### Parameters
`s` Any input string. Note that with all Lua strings, these may contain all character values including "\0".
#### Returns
Nothing