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nodemcu-firmware/app/modules/pipe.c

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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 2. (Slot
** 1 of the table is reserved for the pipe reader function with 0 denoting no
** reader.)
**
** 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 pipe tables also support the undocumented length and tostring
** operators for debugging puposes, so if p is a pipe then #p[i] gives the
** effective length of pipe slot i and printing p[i] gives its contents.
**
** The pipe library also supports the automatic scheduling of a reader task.
** This is declared by including a Lua CB function and an optional prioirty for
** it to execute at in the pipe.create() call. The reader task may or may not
** empty the FIFO (and there is also nothing to stop the task also writing to
** the FIFO. The reader automatically reschedules itself if the pipe contains
** unread content.
**
** The reader tasks may be interleaved with other tasks that write to the pipe
** and others that don't. Any task writing to the pipe will also trigger the
** posting of a read task if one is not already pending. In this way at most
** only one pending reader task is pending, and this prevents overrun of the
** task queueing system.
**
** Implementation Notes:
**
** - The Pipe slot 1 is used to store the Lua CB function reference of the
** reader task. Note that is actually an auxiliary wrapper around the
** supplied Lua CB function, and this wrapper also uses upvals to store
** internal pipe state. The remaining slots are the Userdata buffer chunks.
**
** - This internal state needs to be shared with the pipe_write function, but a
** limitation of Lua 5.1 is that C functions cannot share upvals; to avoid
** this constraint, this function is also denormalised to act as the
** pipe_write function: if Arg1 is the pipe then its a pipe:write() otherwise
** its a CB wrapper.
**
** Also note that the pipe module is used by the Lua VM and therefore the create
** read, and unread methods are exposed as directly callable C functions. (Write
** is available through pipe[1].)
**
** 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;
#define AT_TAIL 0x00
#define AT_HEAD 0x01
#define WRITING 0x02
static buffer_t *checkPipeUD (lua_State *L, int ndx);
static buffer_t *newPipeUD(lua_State *L, int ndx, int n);
static int pipe_write_aux(lua_State *L);
LROT_TABLE(pipe_meta);
/* Validation and utility functions */
// [-0, +0, v]
static buffer_t *checkPipeTable (lua_State *L, int tbl, int flags) {
int m = lua_gettop(L), n = lua_objlen(L, tbl);
if (lua_istable(L, tbl) && 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 == 1) {
ud = (flags & WRITING) ? newPipeUD(L, tbl, 2) : NULL;
} else {
int i = flags & AT_HEAD ? 2 : 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_argerror(L, tbl, "pipe table");
return NULL; /* NORETURN avoid compiler error */
}
static buffer_t *checkPipeUD (lua_State *L, int ndx) { // [-0, +0, v]
luaL_checktype(L, ndx, LUA_TUSERDATA); /* NORETURN on error */
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 */
}
}
}
/* Create new buffer chunk at `n` in the table which is at stack `ndx` */
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[n] = new UD */
return ud; /* ud points to new T[n] */
}
#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;
}
/*
** Read CB Initiator AND pipe_write. If arg1 == the pipe, then this is a pipe
** write(); otherwise it is the Lua CB wapper for the task post. This botch
** allows these two functions to share Upvals within the Lua 5.1 VM:
*/
#define UVpipe lua_upvalueindex(1) // The pipe table object
#define UVfunc lua_upvalueindex(2) // The CB's Lua function
#define UVprio lua_upvalueindex(3) // The task priority
#define UVstate lua_upvalueindex(4) // Pipe state;
#define CB_NOT_USED 0
#define CB_ACTIVE 1
#define CB_WRITE_UPDATED 2
#define CB_QUIESCENT 4
/*
** Note that nothing precludes the Lua CB function from itself writing to the
** pipe and in this case this routine will call itself recursively.
**
** The Lua CB itself takes the pipe object as a parameter and returns an
** optional boolean to force or to suppress automatic retasking if needed. If
** omitted, then the default is to repost if the pipe is not empty, otherwise
** the task chain is left to lapse.
*/
static int pipe_write_and_read_poster (lua_State *L) {
int state = lua_tointeger(L, UVstate);
if (lua_rawequal(L, 1, UVpipe)) {
/* arg1 == the pipe, so this was invoked as a pipe_write() */
if (pipe_write_aux(L) && state && !(state & CB_WRITE_UPDATED)) {
/*
* if this resulted in a write and not already in a CB and not already
* toggled the write update then post the task
*/
state |= CB_WRITE_UPDATED;
lua_pushinteger(L, state);
lua_replace(L, UVstate); /* Set CB state write updated flag */
if (state == CB_QUIESCENT | CB_WRITE_UPDATED) {
lua_rawgeti(L, 1, 1); /* Get CB ref from pipe[1] */
luaL_posttask(L, (int) lua_tointeger(L, UVprio)); /* and repost task */
}
}
} else if (state != CB_NOT_USED) {
/* invoked by the luaN_taskpost() so call the Lua CB */
int repost; /* can take the values CB_WRITE_UPDATED or 0 */
lua_pushinteger(L, CB_ACTIVE); /* CB state set to active only */
lua_replace(L, UVstate);
lua_pushvalue(L, UVfunc); /* Lua CB function */
lua_pushvalue(L, UVpipe); /* pipe table */
lua_call(L, 1, 1); /* Errors are thrown back to caller */
/*
* On return from the Lua CB, the task is never reposted if the pipe is empty.
* If it is not empty then the Lua CB return status determines when reposting
* occurs:
* - true = repost
* - false = don't repost
* - nil = only repost if there has been a write update.
*/
if (lua_isboolean(L,-1)) {
repost = (lua_toboolean(L, -1) == true &&
lua_objlen(L, UVpipe) > 1) ? CB_WRITE_UPDATED : 0;
} else {
repost = state & CB_WRITE_UPDATED;
}
state = CB_QUIESCENT | repost;
lua_pushinteger(L, state); /* Update the CB state */
lua_replace(L, UVstate);
if (repost) {
lua_rawgeti(L, UVpipe, 1); /* Get CB ref from pipe[1] */
luaL_posttask(L, (int) lua_tointeger(L, UVprio)); /* and repost task */
}
}
return 0;
}
/* Lua callable methods. Since the metatable is linked to both the pipe table */
/* and the userdata entries the __len & __tostring functions must handle both */
// Lua: buf = pipe.create()
int pipe_create(lua_State *L) {
int prio = -1;
lua_settop(L, 2); /* fix stack sze as 2 */
if (!lua_isnil(L, 1)) {
luaL_checktype(L, 1, LUA_TFUNCTION); /* non-nil arg1 must be a function */
if (lua_isnil(L, 2)) {
prio = LUA_TASK_MEDIUM;
} else {
prio = (int) lua_tointeger(L, 2);
luaL_argcheck(L, prio >= LUA_TASK_LOW &&
prio <= LUA_TASK_HIGH, 2,
"invalid priority");
}
}
lua_createtable (L, 1, 0); /* create pipe table */
lua_pushrotable(L, LROT_TABLEREF(pipe_meta));
lua_setmetatable(L, -2); /* set pipe table's metabtable to pipe_meta */
lua_pushvalue(L, -1); /* UV1: pipe object */
lua_pushvalue(L, 1); /* UV2: CB function */
lua_pushinteger(L, prio); /* UV3: task priority */
lua_pushinteger(L, prio == -1 ? CB_NOT_USED : CB_QUIESCENT);
lua_pushcclosure(L, pipe_write_and_read_poster, 4); /* aux func for C task */
lua_rawseti(L, -2, 1); /* and write to T[1] */
return 1; /* return the table */
}
// len = #pipeobj[i]
static int pipe__len (lua_State *L) {
if (lua_istable(L, 1)) {
lua_pushinteger(L, lua_objlen(L, 1));
} else {
buffer_t *ud = checkPipeUD(L, 1);
lua_pushinteger(L, ud->end - ud->start);
}
return 1;
}
//Lua s = pipeUD:tostring()
static int pipe__tostring (lua_State *L) {
if (lua_istable(L, 1)) {
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;
}
// Lua: rec = p:read(end_or_delim) // also [-2, +1,- ]
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--;
n = 0; /* force loop exit because delim found */
}
} 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 = 2; i < nUD; i++) { /* for i = 2, 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>1) {
lua_rawgeti(L, 1, 2);
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)
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 | WRITING);
do {
int used = ud->end - ud->start;
int lrem = LUAL_BUFFERSIZE-used;
if (used == LUAL_BUFFERSIZE) {
/* If the current UD is full insert a new UD at T[2] */
int i, nUD = lua_objlen(L, 1);
for (i = nUD; i > 1; i--) { /* for i = nUD,1,-1 */
lua_rawgeti(L, 1, i); lua_rawseti(L, 1, i+1); /* T[i+1] = T[i] */
}
ud = newPipeUD(L, 1, 2);
used = 0; lrem = LUAL_BUFFERSIZE;
/* Filling leftwards; make this chunk "empty but at the right end" */
ud->start = ud->end = LUAL_BUFFERSIZE;
} else if (ud->start < l) {
/* If the unread can't fit it before the start, shift content to end */
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're here then the remaining string is strictly longer than the */
/* remaining buffer space; 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.
* Here, ud != NULL and 0 <= l <= ud->start */
ud->start -= l;
memcpy(ud->buf + ud->start, s, l);
return 0;
}
// Lua: buf:write(some_string)
static int pipe_write_aux(lua_State *L) {
size_t l = INVALID_LEN;
const char *s = lua_tolstring(L, 2, &l);
//dbg_printf("pipe write(%u): %s", l, s);
if (l==0)
return false;
luaL_argcheck(L, l != INVALID_LEN, 2, "must be a string");
buffer_t *ud = checkPipeTable(L, 1, AT_TAIL | WRITING);
do {
int used = ud->end - ud->start;
if (used == LUAL_BUFFERSIZE) {
/* If the current UD is full insert a new UD at T[end] */
ud = newPipeUD(L, 1, lua_objlen(L, 1)+1);
used = 0;
} else if (LUAL_BUFFERSIZE - ud->end < l) {
/* If the write can't fit it at the end then shift content to the 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 true;
}
// 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;
}
// return number of records
static int pipe_nrec (lua_State *L) {
lua_pushinteger(L, lua_objlen(L, 1) - 1);
return 1;
}
LROT_BEGIN(pipe_funcs, NULL, 0)
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( nrec, pipe_nrec )
LROT_END(pipe_funcs, NULL, 0)
/* Using a index func is needed because the write method is at pipe[1] */
static int pipe__index(lua_State *L) {
lua_settop(L,2);
const char *k=lua_tostring(L,2);
if(!strcmp(k,"write")){
lua_rawgeti(L, 1, 1);
} else {
lua_pushrotable(L, LROT_TABLEREF(pipe_funcs));
lua_replace(L, 1);
lua_rawget(L, 1);
}
return 1;
}
LROT_BEGIN(pipe_meta, NULL, LROT_MASK_INDEX)
LROT_FUNCENTRY( __index, pipe__index)
LROT_FUNCENTRY( __len, pipe__len )
LROT_FUNCENTRY( __tostring, pipe__tostring )
LROT_END(pipe_meta, NULL, LROT_MASK_INDEX)
LROT_BEGIN(pipe, NULL, 0)
LROT_FUNCENTRY( create, pipe_create )
LROT_END(pipe, NULL, 0)
NODEMCU_MODULE(PIPE, "pipe", pipe, NULL);
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