/* Store I/O Copyright (C) 1995 Free Software Foundation, Inc. Written by Miles Bader This file is part of the GNU Hurd. The GNU Hurd 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 2, or (at your option) any later version. The GNU Hurd 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, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include #include "store.h" /* Returns in RUNS the tail of STORE's run list, who's first run contains ADDR, and is not a whole, and in RUNS_END a pointer pointing at the end of the run list. Returns the offset within it at which ADDR occurs. */ static inline off_t store_find_first_run (struct store *store, off_t addr, off_t **runs, off_t **runs_end) { off_t *tail = store->runs, *tail_end = tail + store->runs_len; /* XXX: this isn't going to be very efficient if RUNS is very complex... But it should do dandy if it's short. For long run lists, we could do a binary search or something. */ while (tail < tail_end) { off_t run_blocks = tail[1]; if (run_blocks > addr) { *runs = tail; *runs_end = tail_end; return addr; } /* Not to the right place yet, move on... */ addr -= run_blocks; tail += 2; } return -1; } /* Write LEN bytes from BUF to STORE at ADDR. Returns the amount written in AMOUNT. ADDR is in BLOCKS (as defined by STORE->block_size). */ error_t store_write (struct store *store, off_t addr, char *buf, size_t len, size_t *amount) { error_t err; off_t *runs, *runs_end; store_write_meth_t write = store->meths->write; addr = store_find_first_run (store, addr, &runs, &runs_end); if (addr < 0) err = EIO; else if (runs[1] >= len) /* The first run has it all... */ err = (*write)(store, runs[0] + addr, buf, len, amount); else /* ARGH, we've got to split up the write ... */ { mach_msg_type_number_t written; /* Write the initial bit in the first run. Errors here are returned. */ err = (*write)(store, runs[0] + addr, buf, runs[1], &written); if (!err && written == runs[1]) /* Wrote the first bit successfully, now do the rest. Any errors will just result in a short write. */ { int block_shift = store->log2_block_size; buf += written; len -= written; runs += 2; while (runs != runs_end) { off_t run_addr = runs[0]; off_t run_blocks = runs[1]; if (run_addr < 0) /* A hole! Can't write here. Must stop. */ break; else /* Ok, we can write in this run, at least a bit. */ { mach_msg_type_number_t seg_written; off_t run_len = (run_blocks << block_shift); size_t seg_len = run_len > len ? len : run_len; err = (*write)(store, run_addr, buf, seg_len, &seg_written); if (err) break; /* Ack */ written += seg_written; if (seg_written < run_len) break; /* Didn't use up the run, we're done. */ len -= seg_written; if (len == 0) break; /* Nothing left to write! */ buf += written; } runs += 2; } } *amount = written; } return err; } /* Read AMOUNT bytes from STORE at ADDR into BUF & LEN (which following the usual mach buffer-return semantics) to STORE at ADDR. ADDR is in BLOCKS (as defined by STORE->block_size). */ error_t store_read (struct store *store, off_t addr, size_t amount, char **buf, size_t *len) { error_t err; off_t *runs, *runs_end; store_read_meth_t read = store->meths->read; addr = store_find_first_run (store, addr, &runs, &runs_end); if (addr < 0) err = EIO; else if (runs[1] >= amount) /* The first run has it all... */ err = (*read)(store, runs[0] + addr, amount, buf, len); else /* ARGH, we've got to split up the read ... This isn't fun. */ { int all; /* WHOLE_BUF and WHOLE_BUF_LEN will point to a buff that's large enough to hold the entire request. This is initially whatever the user passed in, but we'll change it as necessary. */ char *whole_buf = *buf, *buf_end = whole_buf; size_t whole_buf_len = *len; int block_shift = store->log2_block_size; /* Read LEN bytes from the store address ADDR into BUF_END. BUF_END and AMOUNT are adjusted by the amount actually read. Whether or not the amount read is the same as what was request is returned in ALL. */ inline error_t seg_read (off_t addr, off_t len, int *all) { /* SEG_BUF and SEG_LEN are the buffer for a particular bit of the whole (within one run). */ char *seg_buf = buf_end; size_t seg_buf_len = len; error_t err = (*read)(store, addr, len, &seg_buf, &seg_buf_len); if (!err) { /* If for some bizarre reason, the underlying storage chose not to use the buffer space we so kindly gave it, bcopy it to that space. */ if (seg_buf != buf_end) bcopy (seg_buf, buf_end, seg_buf_len); buf_end += seg_buf_len; amount -= seg_buf_len; *all = (seg_buf_len == len); } return err; } if (whole_buf_len < amount) /* Not enough room in the user's buffer to hold everything, better make room. */ { whole_buf_len = amount; err = vm_allocate (mach_task_self (), (vm_address_t *)&whole_buf, amount, 1); if (err) return err; /* Punt early, there's nothing to clean up. */ } err = seg_read (runs[0] + addr, runs[1] << block_shift, &all); if (!err && all) { runs += 2; while (!err && runs != runs_end && all) { off_t run_addr = runs[0]; off_t run_blocks = runs[1]; if (run_addr < 0) /* A hole! Can't read here. Must stop. */ break; else if (amount == 0) break; else { off_t run_len = (run_blocks << block_shift); off_t seg_len = run_len > amount ? amount : run_len; err = seg_read (run_addr, seg_len, &all); } runs +=2; } } /* The actual amount read. */ *len = whole_buf + whole_buf_len - buf_end; if (*len > 0) err = 0; /* Return a short read instead of an error. */ /* Deallocate any amount of WHOLE_BUF we didn't use. */ if (whole_buf != *buf) if (err) vm_deallocate (mach_task_self (), (vm_address_t)whole_buf, whole_buf_len); else { vm_size_t unused = whole_buf_len - round_page (*len); if (unused) vm_deallocate (mach_task_self (), (vm_address_t)whole_buf + whole_buf_len - unused, unused); *buf = whole_buf; } } return err; }