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kernel: remove input stream stack
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Instead of pre-allocating a fixed number of TypInputFile instances on each
thread, we allocate the required storage dynamically on the stack. This
arguably makes it easier to reason about the global state of GAP.

It also enables future simplifications and improvements, e.g. further
decoupling the input file code from the line buffering and potential
optimizations resulting from that.
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@fingolfin
fingolfin committed Oct 12, 2020
1 parent c955ca0 commit 9723019
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Showing 7 changed files with 146 additions and 194 deletions.
2 changes: 1 addition & 1 deletion src/common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -205,7 +205,7 @@ typedef const struct init_info StructInitInfo;
*T TypInputFile . . . . . . . . . . structure of an open input file, local
**
** This is a forward declaration so that TypInputFile can be used in header
** files. The actual declaration is in io.c and is private.
** files. The actual declaration is in io.h.
*/
typedef struct TypInputFile TypInputFile;

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18 changes: 9 additions & 9 deletions src/gap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -197,14 +197,13 @@ static Obj Shell(Obj context,
if (!OpenOutput(outFile, FALSE))
ErrorQuit("SHELL: can't open outfile %s",(Int)outFile,0);

if(!OpenInput(inFile))
TypInputFile input = { 0 };
if (!OpenInput(&input, inFile))
{
CloseOutput();
ErrorQuit("SHELL: can't open infile %s",(Int)inFile,0);
}

TypInputFile * input = GetCurrentInput();

oldPrintObjState = SetPrintObjState(0);

while ( 1 ) {
Expand Down Expand Up @@ -255,7 +254,7 @@ static Obj Shell(Obj context,
STATE(ErrorLVars) = errorLVars;

/* now read and evaluate and view one command */
status = ReadEvalCommand(errorLVars, input, &evalResult, &dualSemicolon);
status = ReadEvalCommand(errorLVars, &input, &evalResult, &dualSemicolon);
if (STATE(UserHasQUIT))
break;

Expand Down Expand Up @@ -310,14 +309,14 @@ static Obj Shell(Obj context,

if (STATE(UserHasQuit))
{
FlushRestOfInputLine(input);
FlushRestOfInputLine(&input);
STATE(UserHasQuit) = 0; /* quit has done its job if we are here */
}

}

SetPrintObjState(oldPrintObjState);
CloseInput();
CloseInput(&input);
CloseOutput();
STATE(ErrorLLevel) = oldErrorLLevel;
SetRecursionDepth(oldRecursionDepth);
Expand Down Expand Up @@ -402,11 +401,12 @@ int realmain( int argc, char * argv[] )
read of init.g somehow*/
/* maybe compile in which case init.g got skipped */
if ( SyCompilePlease ) {
if ( ! OpenInput(SyCompileInput) ) {
TypInputFile input = { 0 };
if ( ! OpenInput(&input, SyCompileInput) ) {
return 1;
}
func = READ_AS_FUNC();
if (!CloseInput()) {
func = READ_AS_FUNC(&input);
if (!CloseInput(&input)) {
return 2;
}
crc = SyGAPCRC(SyCompileInput);
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167 changes: 33 additions & 134 deletions src/io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -44,57 +44,6 @@
#include <limits.h>


/****************************************************************************
**
*T TypInputFile . . . . . . . . . . structure of an open input file, local
**
** 'TypInputFile' describes the information stored for open input files.
*/
struct TypInputFile {
// non-zero if input comes from a stream
BOOL isstream;

// non-zero if input come from a string stream
BOOL isstringstream;

// if input comes from a stream, this points to a GAP IsInputStream object
Obj stream;

// holds the file identifier received from 'SyFopen' and which is passed
// to 'SyFgets' and 'SyFclose' to identify this file
Int file;

// the name of the file; this is only used in error messages
char name[256];

//
UInt gapnameid;

// a buffer that holds the current input line; always terminated
// by the character '\0'. Because 'line' holds only part of the line for
// very long lines the last character need not be a <newline>.
// The actual line data starts in line[1]; the first byte line[0]
// is reserved for the "pushback buffer" used by PEEK_NEXT_CHAR.
char line[32768];

// the next line from the stream as GAP string
Obj sline;

//
Int spos;

//
BOOL echo;

// pointer to the current character within the current line
char * ptr;

// the number of the current line; used in error messages
Int number;

};


/****************************************************************************
**
*T TypOutputFiles . . . . . . . . . structure of an open output file, local
Expand Down Expand Up @@ -149,16 +98,11 @@ enum {

struct IOModuleState {

// The stack of the open input files
TypInputFile * InputStack[MAX_OPEN_FILES];
int InputStackPointer;

// The stack of open output files
TypOutputFile * OutputStack[MAX_OPEN_FILES];
int OutputStackPointer;

// A pointer to the current input file. It points to the top of the stack
// 'InputFiles'.
// A pointer to the current input file
TypInputFile * Input;

// A pointer to the current output file. It points to the top of the
Expand Down Expand Up @@ -258,9 +202,9 @@ Char PEEK_NEXT_CHAR(TypInputFile * input)
// store the current character
char c = *input->ptr;

// read next character; this will increment IO()->Input->ptr and then
// read next character; this will increment input->ptr and then
// possibly read in new line data, and so even might end up reseting
// IO()->Input->ptr to point at the start of the line buffer, which is
// input->ptr to point at the start of the line buffer, which is
// equal to Input->line+1
char next = GetNextChar(input);

Expand Down Expand Up @@ -360,23 +304,9 @@ Obj GetCachedFilename(UInt id)
*/

#if !defined(HPCGAP)
static TypInputFile InputFiles[MAX_OPEN_FILES];
static TypOutputFile OutputFiles[MAX_OPEN_FILES];
#endif

static TypInputFile * PushNewInput(void)
{
GAP_ASSERT(IO()->InputStackPointer < MAX_OPEN_FILES);
const int sp = IO()->InputStackPointer++;
#ifdef HPCGAP
if (!IO()->InputStack[sp]) {
IO()->InputStack[sp] = AllocateMemoryBlock(sizeof(TypInputFile));
}
#endif
GAP_ASSERT(IO()->InputStack[sp]);
return IO()->InputStack[sp];
}

static TypOutputFile * PushNewOutput(void)
{
GAP_ASSERT(IO()->OutputStackPointer < MAX_OPEN_FILES);
Expand All @@ -394,22 +324,22 @@ static TypOutputFile * PushNewOutput(void)
static GVarDescriptor DEFAULT_INPUT_STREAM;
static GVarDescriptor DEFAULT_OUTPUT_STREAM;

static UInt OpenDefaultInput(void)
static UInt OpenDefaultInput(TypInputFile * input)
{
Obj func, stream;
stream = TLS(DefaultInput);
if (stream)
return OpenInputStream(stream, FALSE);
return OpenInputStream(input, stream, FALSE);
func = GVarOptFunction(&DEFAULT_INPUT_STREAM);
if (!func)
return OpenInput("*stdin*");
return OpenInput(input, "*stdin*");
stream = CALL_0ARGS(func);
if (!stream)
ErrorQuit("DEFAULT_INPUT_STREAM() did not return a stream", 0, 0);
if (IsStringConv(stream))
return OpenInput(CONST_CSTR_STRING(stream));
return OpenInput(input, CONST_CSTR_STRING(stream));
TLS(DefaultInput) = stream;
return OpenInputStream(stream, FALSE);
return OpenInputStream(input, stream, FALSE);
}

static UInt OpenDefaultOutput(void)
Expand Down Expand Up @@ -461,21 +391,18 @@ static UInt OpenDefaultOutput(void)
** '*stdin*' for that purpose. This file on the other hand cannot be
** closed by 'CloseInput'.
*/
UInt OpenInput (
const Char * filename )
UInt OpenInput(TypInputFile * input, const Char * filename)
{
Int file;
GAP_ASSERT(input);

/* fail if we can not handle another open input file */
if (IO()->InputStackPointer == MAX_OPEN_FILES)
return 0;
Int file;

#ifdef HPCGAP
/* Handle *defin*; redirect *errin* to *defin* if the default
* channel is already open. */
if (streq(filename, "*defin*") ||
(streq(filename, "*errin*") && TLS(DefaultInput)))
return OpenDefaultInput();
return OpenDefaultInput(input);
#endif

/* try to open the input file */
Expand All @@ -484,10 +411,10 @@ UInt OpenInput (
return 0;

/* enter the file identifier and the file name */
TypInputFile * input = IO()->Input = PushNewInput();
memset(input, 0, sizeof(TypInputFile));
input->prev = IO()->Input;
input->isstream = FALSE;
input->file = file;
input->name[0] = '\0';

// enable echo for stdin and errin
if (streq("*errin*", filename) || streq("*stdin*", filename))
Expand All @@ -504,6 +431,8 @@ UInt OpenInput (
input->ptr = input->line + 1;
input->number = 1;

IO()->Input = input;

/* indicate success */
return 1;
}
Expand All @@ -515,14 +444,13 @@ UInt OpenInput (
**
** The same as 'OpenInput' but for streams.
*/
UInt OpenInputStream(Obj stream, BOOL echo)
UInt OpenInputStream(TypInputFile * input, Obj stream, BOOL echo)
{
/* fail if we can not handle another open input file */
if (IO()->InputStackPointer == MAX_OPEN_FILES)
return 0;
GAP_ASSERT(input);

/* enter the file identifier and the file name */
TypInputFile * input = IO()->Input = PushNewInput();
memset(input, 0, sizeof(TypInputFile));
input->prev = IO()->Input;
input->isstream = TRUE;
input->stream = stream;
input->isstringstream = (CALL_1ARGS(IsStringStream, stream) == True);
Expand All @@ -544,6 +472,8 @@ UInt OpenInputStream(Obj stream, BOOL echo)
input->ptr = input->line + 1;
input->number = 1;

IO()->Input = input;

/* indicate success */
return 1;
}
Expand All @@ -564,39 +494,22 @@ UInt OpenInputStream(Obj stream, BOOL echo)
** Calling 'CloseInput' if the corresponding 'OpenInput' call failed will
** close the current output file, which will lead to very strange behaviour.
*/
UInt CloseInput ( void )
UInt CloseInput(TypInputFile * input)
{
/* refuse to close the initial input file */
#ifdef HPCGAP
// In HPC-GAP, only for the main thread.
if (TLS(threadID) != 0) {
if (IO()->InputStackPointer <= 0)
return 0;
} else
#else
if (IO()->InputStackPointer <= 1)
return 0;
#endif
GAP_ASSERT(input);
GAP_ASSERT(input == IO()->Input);

/* close the input file */
if (!IO()->Input->isstream) {
SyFclose(IO()->Input->file);
// close the input file
if (!input->isstream) {
SyFclose(input->file);
}

/* don't keep GAP objects alive unnecessarily */
memset(IO()->Input, 0, sizeof(TypInputFile));
// revert to previous input
IO()->Input = input->prev;

/* revert to last file */
const int sp = --IO()->InputStackPointer;
#ifdef HPCGAP
if (sp == 0) {
IO()->Input = NULL;
return 1;
}
#endif
IO()->Input = IO()->InputStack[sp - 1];
// don't keep GAP objects alive unnecessarily
memset(input, 0, sizeof(TypInputFile));

/* indicate success */
return 1;
}

Expand Down Expand Up @@ -2064,8 +1977,6 @@ static Int InitLibrary (

#if !defined(HPCGAP)
static Char OutputFilesStreamCookie[MAX_OPEN_FILES][9];
static Char InputFilesStreamCookie[MAX_OPEN_FILES][9];
static Char InputFilesSlineCookie[MAX_OPEN_FILES][9];
#endif

static Int InitKernel (
Expand All @@ -2078,12 +1989,10 @@ static Int InitKernel (

#if !defined(HPCGAP)
for (Int i = 0; i < MAX_OPEN_FILES; i++) {
IO()->InputStack[i] = &InputFiles[i];
IO()->OutputStack[i] = &OutputFiles[i];
}
#endif

OpenInput("*stdin*");
OpenOutput("*stdout*", FALSE);

InitGlobalBag( &FilenameCache, "FilenameCache" );
Expand All @@ -2094,22 +2003,12 @@ static Int InitKernel (
DeclareGVar(&DEFAULT_OUTPUT_STREAM, "DEFAULT_OUTPUT_STREAM");

#else
// Initialize cookies for streams. Also initialize the cookies for the
// GAP strings which hold the latest lines read from the streams and the
// name of the current input file. For HPC-GAP we don't need the cookies
// Initialize cookies for streams. For HPC-GAP we don't need the cookies
// anymore, since the data got moved to thread-local storage.
for (Int i = 0; i < MAX_OPEN_FILES; i++) {
strxcpy(OutputFilesStreamCookie[i], "ostream0", sizeof(OutputFilesStreamCookie[i]));
OutputFilesStreamCookie[i][7] = '0' + i;
InitGlobalBag(&(OutputFiles[i].stream), &(OutputFilesStreamCookie[i][0]));

strxcpy(InputFilesStreamCookie[i], "istream0", sizeof(InputFilesStreamCookie[i]));
InputFilesStreamCookie[i][7] = '0' + i;
InitGlobalBag(&(InputFiles[i].stream), &(InputFilesStreamCookie[i][0]));

strxcpy(InputFilesSlineCookie[i], "isline 0", sizeof(InputFilesSlineCookie[i]));
InputFilesSlineCookie[i][7] = '0' + i;
InitGlobalBag(&(InputFiles[i].sline), &(InputFilesSlineCookie[i][0]));
}

/* tell GASMAN about the global bags */
Expand Down
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