diff options
author | jsdelfino <jsdelfino@13f79535-47bb-0310-9956-ffa450edef68> | 2010-04-17 22:59:51 +0000 |
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committer | jsdelfino <jsdelfino@13f79535-47bb-0310-9956-ffa450edef68> | 2010-04-17 22:59:51 +0000 |
commit | cd904cdd0a82ad3c7859b5bc4365202c320da81f (patch) | |
tree | 45fbd4e5fdb92cdd327dab1775d29ae7d3dc1d5a /sca-cpp/trunk/components/nosqldb/tinycdb.hpp | |
parent | 3d79be04a42d86838a110d679de4004d5b98b789 (diff) |
Strawman implementation of post, put and delete on a tinycdb database, for now just a simplistic rewrite of the db per update.
git-svn-id: http://svn.us.apache.org/repos/asf/tuscany@935274 13f79535-47bb-0310-9956-ffa450edef68
Diffstat (limited to 'sca-cpp/trunk/components/nosqldb/tinycdb.hpp')
-rw-r--r-- | sca-cpp/trunk/components/nosqldb/tinycdb.hpp | 340 |
1 files changed, 340 insertions, 0 deletions
diff --git a/sca-cpp/trunk/components/nosqldb/tinycdb.hpp b/sca-cpp/trunk/components/nosqldb/tinycdb.hpp new file mode 100644 index 0000000000..c2d1f2c50f --- /dev/null +++ b/sca-cpp/trunk/components/nosqldb/tinycdb.hpp @@ -0,0 +1,340 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +/* $Rev$ $Date$ */ + +#ifndef tuscany_tinycdb_hpp +#define tuscany_tinycdb_hpp + +#include <fcntl.h> +#include <cdb.h> + +#include "string.hpp" +#include "list.hpp" +#include "value.hpp" +#include "monad.hpp" +#include "../../modules/scheme/eval.hpp" + +namespace tuscany { +namespace tinycdb { + +/** + * A reallocatable buffer. + */ +class buffer { +public: + operator void*() const throw() { + return buf; + } + + operator unsigned char*() const throw() { + return (unsigned char*)buf; + } + + operator char*() const throw() { + return (char*)buf; + } + +private: + buffer(const unsigned int size, void* buf) : size(size), buf(buf) { + } + + unsigned int size; + void* buf; + + friend const buffer mkbuffer(const unsigned int sz); + friend const buffer mkbuffer(const buffer& b, const unsigned int newsz); + friend const bool free(const buffer& b); +}; + +/** + * Make a new buffer. + */ +const buffer mkbuffer(const unsigned int sz) { + return buffer(sz, malloc(sz)); +} + +/** + * Make a new buffer by reallocating an existing one. + */ +const buffer mkbuffer(const buffer& b, const unsigned int sz) { + if (sz <= b.size) + return b; + return buffer(sz, realloc(b.buf, sz)); +} + +/** + * Free a buffer. + */ +const bool free(const buffer&b) { + ::free(b.buf); + return true; +} + +/** + * Represents a TinyCDB connection. + */ +class TinyCDB { +public: + TinyCDB() : owner(false) { + } + + TinyCDB(const string& file) : owner(true), file(file) { + fd = open(c_str(file), O_RDONLY); + } + + TinyCDB(const TinyCDB& c) : owner(false) { + file = c.file; + fd = c.fd; + } + + ~TinyCDB() { + if (!owner) + return; + if (fd == -1) + return; + close(fd); + } + +private: + bool owner; + string file; + int fd; + + friend const failable<bool> post(const value& key, const value& val, TinyCDB& cdb); + friend const failable<bool> put(const value& key, const value& val, const TinyCDB& cdb); + friend const failable<value> get(const value& key, const TinyCDB& cdb); + friend const failable<bool> del(const value& key, const TinyCDB& cdb); + friend const failable<bool> rewrite(const lambda<failable<bool>(buffer& buf, const unsigned int klen, const unsigned int vlen)>& update, const lambda<failable<bool>(struct cdb_make&)>& finish, TinyCDB& cdb); + friend const failable<bool> rewrite(const lambda<failable<bool>(buffer& buf, const unsigned int klen, const unsigned int vlen)>& update, const lambda<failable<bool>(struct cdb_make&)>& finish, buffer& buf, const int fd, TinyCDB& cdb); +}; + +/** + * Rewrite a database. The given update function is passed each entry, and + * can return true to let the entry added to the new db, false to skip the + * entry, or a failure. + */ +const failable<bool> rewrite(const lambda<failable<bool>(buffer& buf, const unsigned int klen, const unsigned int vlen)>& update, const lambda<failable<bool>(struct cdb_make&)>& finish, buffer& buf, const int fd, TinyCDB& cdb) { + + // Initialize new db structure + struct cdb_make cdbm; + cdb_make_start(&cdbm, fd); + + // Read the db header + unsigned int pos = 0; + if (lseek(cdb.fd, 0, SEEK_SET) != 0) + return mkfailure<bool>("Could not seek to database start"); + if (::read(cdb.fd, buf, 2048) != 2048) + return mkfailure<bool>("Could not read database header"); + pos += 2048; + unsigned int eod = cdb_unpack(buf); + debug(pos, "tinycdb::post::eod"); + + // Read and add the existing entries + while(pos < eod) { + if (eod - pos < 8) + return mkfailure<bool>("Invalid database format, couldn't read entry header"); + if (::read(cdb.fd, buf, 8) != 8) + return mkfailure<bool>("Couldn't read entry header"); + pos += 8; + unsigned int klen = cdb_unpack(buf); + unsigned int vlen = cdb_unpack(((unsigned char*)buf) + 4); + unsigned int elen = klen + vlen; + + // Read existing entry + buf = mkbuffer(buf, elen); + if (eod - pos < elen) + return mkfailure<bool>("Invalid database format, couldn't read entry"); + if ((unsigned int)::read(cdb.fd, buf, elen) != elen) + return mkfailure<bool>("Couldn't read entry"); + pos += elen; + + // Apply the update function to the entry + debug(string((char*)buf, klen), "tinycdb::post::existing key"); + debug(string(((char*)buf) + klen, vlen), "tinycdb::post::existing value"); + const failable<bool> u = update(buf, klen, vlen); + if (!hasContent(u)) + return u; + + // Skip the entry if the update function returned false + if (u == false) + continue; + + // Add the entry to the new db + if (cdb_make_add(&cdbm, buf, klen, ((unsigned char*)buf)+klen, vlen) == -1) + return mkfailure<bool>("Could not add entry"); + } + if (pos != eod) + return mkfailure<bool>("Invalid database format"); + + // Call the finish function + const failable<bool> f = finish(cdbm); + if (!hasContent(f)) + return f; + + // Save the new db + if (cdb_make_finish(&cdbm) == -1) + return mkfailure<bool>("Could not save database"); + + return true; +} + +const failable<bool> rewrite(const lambda<failable<bool>(buffer& buf, const unsigned int klen, const unsigned int vlen)>& update, const lambda<failable<bool>(struct cdb_make&)>& finish, TinyCDB& cdb) { + if (cdb.fd == -1) + return mkfailure<bool>("Could not open database"); + + // Create a new temporary db file + const char* tmpfile = c_str(cdb.file + ".tmp"); + unlink(tmpfile); + int fd = open(tmpfile, O_RDWR | O_CREAT | O_EXCL | O_NOFOLLOW, 0666); + if (fd == -1) + return mkfailure<bool>("Could not create temporary database"); + + // Rewrite the db, apply the update function to each entry + buffer buf = mkbuffer(2048); + const failable<bool> r = rewrite(update, finish, buf, fd, cdb); + if (!hasContent(r)) { + close(fd); + free(buf); + return r; + } + + // Atomically replace the db and reopen it in read mode + if (rename(tmpfile, c_str(cdb.file)) == -1) + return mkfailure<bool>("Could not rename temporary database"); + close(cdb.fd); + cdb.fd = open(c_str(cdb.file), O_RDONLY); + + return true; +} + +/** + * Post a new item to the database. + */ +const failable<bool> post(const value& key, const value& val, TinyCDB& cdb) { + debug(key, "tinycdb::post::key"); + debug(val, "tinycdb::post::value"); + + const string ks(scheme::writeValue(key)); + const string vs(scheme::writeValue(val)); + + // Process each entry and detect existing key + auto update = [=](buffer& buf, const unsigned int klen, unused const unsigned int vlen)->const failable<bool> { + if (ks == string((char*)buf, klen)) + return mkfailure<bool>("Key already exists"); + return true; + }; + + // Add the new entry to the db + auto finish = [=](struct cdb_make& cdbm)->const failable<bool> { + if (cdb_make_add(&cdbm, c_str(ks), length(ks), c_str(vs), length(vs)) == -1) + return mkfailure<bool>("Could not add entry"); + return true; + }; + + // Rewrite the db + const failable<bool> r = rewrite(update, finish, cdb); + debug(r, "tinycdb::post::result"); + return r; +} + +/** + * Update an item in the database. If the item doesn't exist it is added. + */ +const failable<bool> put(const value& key, const value& val, TinyCDB& cdb) { + debug(key, "tinycdb::put::key"); + debug(val, "tinycdb::put::value"); + + const string ks(scheme::writeValue(key)); + const string vs(scheme::writeValue(val)); + + // Process each entry and skip existing key + auto update = [&](buffer& buf, const unsigned int klen, unused const unsigned int vlen)->const failable<bool> { + if (ks == string((char*)buf, klen)) + return false; + return true; + }; + + // Add the new entry to the db + auto finish = [&](struct cdb_make& cdbm)->const failable<bool> { + if (cdb_make_add(&cdbm, c_str(ks), length(ks), c_str(vs), length(vs)) == -1) + return mkfailure<bool>("Could not add entry"); + return true; + }; + + // Rewrite the db + const failable<bool> r = rewrite(update, finish, cdb); + debug(r, "tinycdb::put::result"); + return r; +} + +/** + * Get an item from the database. + */ +const failable<value> get(const value& key, const TinyCDB& cdb) { + debug(key, "tinycdb::get::key"); + if (cdb.fd == -1) + return mkfailure<value>("Could not open database"); + + const string ks(scheme::writeValue(key)); + + cdbi_t vlen; + if (cdb_seek(cdb.fd, c_str(ks), length(ks), &vlen) <= 0) + return mkfailure<value>("Could not get entry"); + char* data = gc_cnew(vlen + 1); + cdb_bread(cdb.fd, data, vlen); + data[vlen] = '\0'; + const value val(scheme::readValue(string(data))); + + debug(val, "tinycdb::get::result"); + return val; +} + +/** + * Delete an item from the database + */ +const failable<bool> del(const value& key, TinyCDB& cdb) { + debug(key, "tinycdb::delete::key"); + + const string ks(scheme::writeValue(key)); + + // Process each entry and skip existing key + auto update = [=](buffer& buf, const unsigned int klen, unused const unsigned int vlen)->const failable<bool> { + if (ks == string((char*)buf, klen)) + return false; + return true; + }; + + // Nothing to do to finish + auto finish = [=](unused struct cdb_make& cdbm)->const failable<bool> { + // hack: reference a variable from outer scope to workaround GCC internal error + const string xs(ks); + return true; + }; + + // Rewrite the db + const failable<bool> r = rewrite(update, finish, cdb); + debug(r, "tinycdb::delete::result"); + return r; +} + +} +} + +#endif /* tuscany_tinycdb_hpp */ |