From: Ben Pfaff Date: Tue, 2 Mar 2010 06:12:48 +0000 (-0800) Subject: casereader: Factor buffering shim out into separate source file. X-Git-Tag: sav-api~368 X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?p=pspp;a=commitdiff_plain;h=0fbcb6682003e6deb5f517c4d54bada0301a61a1 casereader: Factor buffering shim out into separate source file. This moves the "shim" code out of casereader.c into a separate casereader-shim.[ch] in preparation for using it from procedure.c. This commit also adds an optimization: if the shim reads all of the subreader, then it closes the subreader immediately, instead of waiting for the shim itself to be destroyed. This can allow resources to be freed earlier. This commit also adds a new function casereader_shim_slurp(). This function will be used for the first time in the following commit. --- diff --git a/src/data/automake.mk b/src/data/automake.mk index ebfb680a09..efa0834f55 100644 --- a/src/data/automake.mk +++ b/src/data/automake.mk @@ -28,6 +28,8 @@ src_data_libdata_la_SOURCES = \ src/data/casereader-project.c \ src/data/casereader-provider.h \ src/data/casereader-select.c \ + src/data/casereader-shim.c \ + src/data/casereader-shim.h \ src/data/casereader-translator.c \ src/data/casereader.c \ src/data/casereader.h \ diff --git a/src/data/casereader-shim.c b/src/data/casereader-shim.c new file mode 100644 index 0000000000..9d9dd70527 --- /dev/null +++ b/src/data/casereader-shim.c @@ -0,0 +1,142 @@ +/* PSPP - a program for statistical analysis. + Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include + +#include "data/casereader-shim.h" + +#include + +#include "data/casereader.h" +#include "data/casereader-provider.h" +#include "data/casewindow.h" +#include "data/settings.h" +#include "libpspp/taint.h" + +#include "gl/xalloc.h" + +/* A buffering shim casereader. */ +struct casereader_shim + { + struct casewindow *window; /* Window of buffered cases. */ + struct casereader *subreader; /* Subordinate casereader. */ + }; + +static const struct casereader_random_class shim_class; + +static bool buffer_case (struct casereader_shim *s); + +/* Interposes a buffering shim on READER. + + Returns the new shim. The only legitimate use of the returned + casereader_shim is for calling casereader_shim_slurp(). If READER has no + clones already (which the caller should ensure, if it plans to use the + return value), then the returned casreader_shim is valid for that purpose + until, and only until, the READER's 'destroy' function is called. */ +struct casereader_shim * +casereader_shim_insert (struct casereader *reader) +{ + const struct caseproto *proto = casereader_get_proto (reader); + casenumber case_cnt = casereader_get_case_cnt (reader); + struct casereader_shim *s = xmalloc (sizeof *s); + s->window = casewindow_create (proto, settings_get_workspace_cases (proto)); + s->subreader = casereader_create_random (proto, case_cnt, &shim_class, s); + casereader_swap (reader, s->subreader); + taint_propagate (casewindow_get_taint (s->window), + casereader_get_taint (reader)); + taint_propagate (casereader_get_taint (s->subreader), + casereader_get_taint (reader)); + return s; +} + +/* Reads all of the cases from S's subreader into S's buffer and destroys S's + subreader. (This is a no-op if the subreader has already been + destroyed.) + + Refer to the comment on casereader_shim_insert() for information on when + this function may be used. */ +void +casereader_shim_slurp (struct casereader_shim *s) +{ + while (buffer_case (s)) + continue; +} + +/* Reads a case from S's subreader and appends it to S's window. Returns true + if successful, false at the end of S's subreader or upon an I/O error. */ +static bool +buffer_case (struct casereader_shim *s) +{ + struct ccase *tmp; + + if (s->subreader == NULL) + return false; + + tmp = casereader_read (s->subreader); + if (tmp == NULL) + { + casereader_destroy (s->subreader); + s->subreader = NULL; + return false; + } + + casewindow_push_head (s->window, tmp); + return true; +} + +/* Reads the case at the given 0-based OFFSET from the front of the window into + C. Returns the case if successful, or a null pointer if OFFSET is beyond + the end of file or upon I/O error. The caller must call case_unref() on the + returned case when it is no longer needed. */ +static struct ccase * +casereader_shim_read (struct casereader *reader UNUSED, void *s_, + casenumber offset) +{ + struct casereader_shim *s = s_; + + while (casewindow_get_case_cnt (s->window) <= offset) + if (!buffer_case (s)) + return false; + + return casewindow_get_case (s->window, offset); +} + +/* Destroys S. */ +static void +casereader_shim_destroy (struct casereader *reader UNUSED, void *s_) +{ + struct casereader_shim *s = s_; + casewindow_destroy (s->window); + casereader_destroy (s->subreader); + free (s); +} + +/* Discards CNT cases from the front of S's window. */ +static void +casereader_shim_advance (struct casereader *reader UNUSED, void *s_, + casenumber case_cnt) +{ + struct casereader_shim *s = s_; + casewindow_pop_tail (s->window, case_cnt); +} + +/* Class for the buffered reader. */ +static const struct casereader_random_class shim_class = + { + casereader_shim_read, + casereader_shim_destroy, + casereader_shim_advance, + }; diff --git a/src/data/casereader-shim.h b/src/data/casereader-shim.h new file mode 100644 index 0000000000..704d1d3de1 --- /dev/null +++ b/src/data/casereader-shim.h @@ -0,0 +1,48 @@ +/* PSPP - a program for statistical analysis. + Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#ifndef DATA_CASEREADER_SHIM_H +#define DATA_CASEREADER_SHIM_H 1 + +/* Buffering shim for implementing clone and peek operations. + + The "clone" and "peek" operations aren't implemented by all types of + casereaders, but we have to expose a uniform interface anyhow. The + casereader buffering shim can do this by interposing a buffer on top of an + existing casereader. The shim maintains a window of cases that spans the + positions of the original casereader and all of its clones (the "clone + set"), from the position of the casereader that has read the fewest cases to + the position of the casereader that has read the most. + + Thus, if all of the casereaders in the clone set are at approximately the + same position, only a few cases are buffered and there is little + inefficiency. If, on the other hand, one casereader is not used to read any + cases at all, but another one is used to read all of the cases, the entire + contents of the casereader is copied into the buffer. This still might not + be so inefficient, given that case data in memory is shared across multiple + identical copies, but in the worst case the window implementation will write + cases to disk instead of maintaining them in-memory. + + Casereader buffering shims are inserted automatically on the first call to + casereader_clone() or casereader_peek() for a casereader that does not + support those operations natively. Thus, there is ordinarily little reason + to intentionally insert a shim. */ + +struct casereader; +struct casereader_shim *casereader_shim_insert (struct casereader *); +void casereader_shim_slurp (struct casereader_shim *); + +#endif /* data/casereader-shim.h */ diff --git a/src/data/casereader.c b/src/data/casereader.c index 97b7ceff3d..98c10273b3 100644 --- a/src/data/casereader.c +++ b/src/data/casereader.c @@ -1,5 +1,5 @@ /* PSPP - a program for statistical analysis. - Copyright (C) 2007, 2009 Free Software Foundation, Inc. + Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -16,19 +16,18 @@ #include -#include -#include +#include "data/casereader.h" +#include "data/casereader-provider.h" #include -#include -#include -#include -#include -#include -#include +#include "data/casereader-shim.h" +#include "data/casewriter.h" +#include "libpspp/assertion.h" +#include "libpspp/heap.h" +#include "libpspp/taint.h" -#include "xalloc.h" +#include "gl/xalloc.h" /* A casereader. */ struct casereader @@ -41,8 +40,6 @@ struct casereader void *aux; /* Auxiliary data for class. */ }; -static void insert_shim (struct casereader *); - /* Reads and returns the next case from READER. The caller owns the returned case and must call case_unref on it when its data is no longer needed. Returns a null pointer if cases have @@ -114,7 +111,7 @@ casereader_clone (const struct casereader *reader_) return NULL; if (reader->class->clone == NULL) - insert_shim (reader); + casereader_shim_insert (reader); clone = reader->class->clone (reader, reader->aux); assert (clone != NULL); assert (clone != reader); @@ -175,7 +172,7 @@ casereader_peek (struct casereader *reader, casenumber idx) { struct ccase *c; if (reader->class->peek == NULL) - insert_shim (reader); + casereader_shim_insert (reader); c = reader->class->peek (reader, reader->aux, idx); if (c != NULL) return c; @@ -598,111 +595,6 @@ static const struct casereader_class random_reader_casereader_class = random_reader_peek, }; -/* Buffering shim for implementing clone and peek operations. - - The "clone" and "peek" operations aren't implemented by all - types of casereaders, but we have to expose a uniform - interface anyhow. We do this by interposing a buffering - casereader on top of the existing casereader on the first call - to "clone" or "peek". The buffering casereader maintains a - window of cases that spans the positions of the original - casereader and all of its clones (the "clone set"), from the - position of the casereader that has read the fewest cases to - the position of the casereader that has read the most. - - Thus, if all of the casereaders in the clone set are at - approximately the same position, only a few cases are buffered - and there is little inefficiency. If, on the other hand, one - casereader is not used to read any cases at all, but another - one is used to read all of the cases, the entire contents of - the casereader is copied into the buffer. This still might - not be so inefficient, given that case data in memory is - shared across multiple identical copies, but in the worst case - the window implementation will write cases to disk instead of - maintaining them in-memory. */ - -/* A buffering shim for a non-clonable or non-peekable - casereader. */ -struct shim - { - struct casewindow *window; /* Window of buffered cases. */ - struct casereader *subreader; /* Subordinate casereader. */ - }; - -static const struct casereader_random_class shim_class; - -/* Interposes a buffering shim atop READER. */ -static void -insert_shim (struct casereader *reader) -{ - const struct caseproto *proto = casereader_get_proto (reader); - casenumber case_cnt = casereader_get_case_cnt (reader); - struct shim *b = xmalloc (sizeof *b); - b->window = casewindow_create (proto, settings_get_workspace_cases (proto)); - b->subreader = casereader_create_random (proto, case_cnt, &shim_class, b); - casereader_swap (reader, b->subreader); - taint_propagate (casewindow_get_taint (b->window), - casereader_get_taint (reader)); - taint_propagate (casereader_get_taint (b->subreader), - casereader_get_taint (reader)); -} - -/* Ensures that B's window contains at least CASE_CNT cases. - Return true if successful, false upon reaching the end of B's - subreader or an I/O error. */ -static bool -prime_buffer (struct shim *b, casenumber case_cnt) -{ - while (casewindow_get_case_cnt (b->window) < case_cnt) - { - struct ccase *tmp = casereader_read (b->subreader); - if (tmp == NULL) - return false; - casewindow_push_head (b->window, tmp); - } - return true; -} - -/* Reads the case at the given 0-based OFFSET from the front of - the window into C. Returns the case if successful, or a null - pointer if OFFSET is beyond the end of file or upon I/O error. - The caller must call case_unref() on the returned case when it - is no longer needed. */ -static struct ccase * -shim_read (struct casereader *reader UNUSED, void *b_, - casenumber offset) -{ - struct shim *b = b_; - if (!prime_buffer (b, offset + 1)) - return NULL; - return casewindow_get_case (b->window, offset); -} - -/* Destroys B. */ -static void -shim_destroy (struct casereader *reader UNUSED, void *b_) -{ - struct shim *b = b_; - casewindow_destroy (b->window); - casereader_destroy (b->subreader); - free (b); -} - -/* Discards CNT cases from the front of B's window. */ -static void -shim_advance (struct casereader *reader UNUSED, void *b_, casenumber case_cnt) -{ - struct shim *b = b_; - casewindow_pop_tail (b->window, case_cnt); -} - -/* Class for the buffered reader. */ -static const struct casereader_random_class shim_class = - { - shim_read, - shim_destroy, - shim_advance, - }; static const struct casereader_class casereader_null_class;