just use a single 16bit index
This commit is contained in:
Alain Zscheile
parent
bf9048443b
commit
4e5fd39cc9
12
meson.build
12
meson.build
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@ -1,6 +1,6 @@
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project('y16t 16-field quad tree library', 'c',
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default_options : ['c_std=c17'],
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version : '0.0.0'
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version : '0.0.0',
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license : 'Apache-2.0',
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meson_version : '>=0.50')
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@ -10,9 +10,17 @@ liby16t = shared_library('y16t',
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files('y16t.c'),
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version : '0.0.0',
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c_args : ['-fno-plt', '-fno-unwind-tables', '-fno-exceptions', '-Werror=return-type'],
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include_directories : include_directories('.')
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include_directories : include_directories('.'),
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install : true)
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executable('y16t-printall',
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files('y16t_printall.c'),
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link_with : [liby16t],
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c_args : ['-fno-plt', '-fno-unwind-tables', '-fno-exceptions', '-Werror=return-type'],
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include_directories : include_directories('.'),
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install : true
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)
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pkg_mod = import('pkgconfig')
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pkg_mod.generate(
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libraries : [liby16t],
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101
y16t.c
101
y16t.c
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@ -1,37 +1,86 @@
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// SPDX-License-Identifier: ISC
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#include "y16t.h"
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#include <arpa/inet.h>
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#include <errno.h>
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// conversion to ις-points interleaved coordinates
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static __attribute__((pure))
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uint8_t y16t_loc2blk_coords(
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const y16t_location_t loc, const uint32_t offset
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) {
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const uint32_t byteoffset = offset >> 1;
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const uint8_t shiftval = 4 * (1 - offset & 1);
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const uint8_t xres = (loc.x[byteoffset] >> shiftval) & 15;
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const uint8_t yres = (loc.y[byteoffset] >> shiftval) & 15;
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return (xres << 4) | yres;
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uint16_t y16t_interleave2(const uint8_t x, const uint8_t y)
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{
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return
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((uint16_t)((x & 0x55) | (y & 0xaa)) << 8)
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(uint16_t)((x & 0xaa) | (y & 0x55))
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;
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}
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void y16t_lookup(
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y16t_lookup_t * ret,
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const uint32_t * data,
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const size_t datalen,
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const y16t_location_t * loc
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) {
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const size_t datalen_blks = datalen >> 8;
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const y16t_location_t loc_ = *loc;
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size_t datoffset = ret->datoffset;
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static __attribute__((pure))
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uint32_t y16t_table_at(const uint8_t x, const uint8_t y)
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{
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return ((uint32_t)y16t_interleave2(x, y)) << 2;
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}
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for ( ; /* bounds checks */ ret->inpoffset < loc_.xylen && datoffset < datalen_blks; ) {
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datoffset = ntohl(data[(datoffset << 8) | y16t_loc2blk_coords(loc_, ret->inpoffset)]);
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ret->inpoffset += 1;
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if(0 == datoffset) {
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// NULL pointer
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break;
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}
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int y16t_idx_lookup(
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FILE *fh,
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uint8_t x,
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uint8_t y,
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uint32_t *result
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) {
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const uint32_t key = y16t_table_at(x, y);
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if(fseek(fh, (long)key, SEEK_SET) == -1)
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return -EIO;
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if(fread(result, 4, 1, fh) != 1)
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return -EIO;
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return 0;
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}
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int y16t_idx_update(
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FILE *fh,
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const uint8_t x,
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const uint8_t y,
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const uint32_t newval
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) {
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const uint32_t key = y16t_table_at(x, y);
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if(fseek(fh, (long)key, SEEK_SET) == -1)
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return -EIO;
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if(fwrite(&newval, 4, 1, fh) != 1)
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return -EIO;
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return 0;
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}
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int y16t_idx_foreach_x(
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FILE *fh,
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uint8_t y,
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int (*callback)(uint32_t, void*),
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void *context
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) {
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for (uint16_t x = 0; x < 0xff; ++x) {
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uint32_t value = 0;
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int tmp = y16t_idx_lookup(fh, x, y, &value);
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if(tmp != 0) return tmp;
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tmp = callback(value, context);
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if(tmp != 0) return tmp;
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}
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ret->datoffset = datoffset;
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return 0;
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}
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int y16t_idx_foreach_y(
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FILE *fh,
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uint8_t x,
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int (*callback)(uint32_t, void*),
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void *context
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) {
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for (uint16_t y = 0; y < 0xff; ++y) {
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uint32_t value = 0;
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int tmp = y16t_idx_lookup(fh, x, y, &value);
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if(tmp != 0) return tmp;
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tmp = callback(value, context);
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if(tmp != 0) return tmp;
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}
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return 0;
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}
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63
y16t.h
63
y16t.h
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@ -2,33 +2,40 @@
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#pragma once
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#include <inttypes.h>
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#include <stddef.h>
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#include <stdio.h>
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typedef struct {
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uint8_t *x;
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uint8_t *y;
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// x and y should have the same length, and xylen = bytescount * 2
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uint32_t xylen;
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} y16t_location_t;
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typedef struct {
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// the offset indicates how far the lookup could traverse the tree
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uint32_t inpoffset;
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// the final data pointer, it doesn't have to be aligned to block boundaries
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// if it ends up at the starting point, but the offset isn't 0,
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// then a NULL pointer was hit
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size_t datoffset;
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} y16t_lookup_t;
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// @param ret ... the starting point; gets updated to the latest via the given path
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// reachable point
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// @param data ... a pointer to a mmap-ed file. we convert pointers inside of the file
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// from network byte order to host byte order before following them.
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// @param datalen ... the length of the block that data points to, in 4 byte units (= file size in bytes / 4)
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__attribute__((pure, nonnull))
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void y16t_lookup(
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y16t_lookup_t * ret,
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const uint32_t * data,
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const size_t datalen,
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const y16t_location_t * loc
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// try to lookup the given coordinates, and return the corresponding location
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// via `result`.
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// the file given as `fh` is expected to be at least 256KiB large
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// returns a negative errno number in case of failure
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__attribute__((nonnull))
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int y16t_idx_lookup(
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FILE *fh,
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uint8_t x,
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uint8_t y,
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uint32_t *result
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);
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// update a table entry.
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__attribute__((nonnull))
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int y16t_idx_update(
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FILE *fh,
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uint8_t x,
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uint8_t y,
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uint32_t newval
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);
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// iterate over columns or rows
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int y16t_idx_foreach_x(
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FILE *fh,
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uint8_t y,
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int (*callback)(uint32_t, void*),
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void *context
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);
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int y16t_idx_foreach_y(
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FILE *fh,
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uint8_t χ,
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int (*callback)(uint32_t, void*),
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void *context
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);
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32
y16t_printall.c
Normal file
32
y16t_printall.c
Normal file
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@ -0,0 +1,32 @@
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#include "y16t.h"
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#include <stdlib.h>
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#include <stdio.h>
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int printall_fecb(uint32_t x, void*)
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{
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printf("%08x\n", x);
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return 0;
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}
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int main(int argc, char *argv[])
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{
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if(argc < 4) {
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fprintf(stderr, "USAGE: y16t-print FILE x|y VALUE\n");
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return -1;
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}
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FILE *fh = fopen(argv[1], "r");
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if(!fh) {
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fprintf(stderr, "ERROR: unable to open file\n");
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return -1;
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}
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uint8_t value = atoi(argv[3]);
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switch(argv[2][0]) {
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case 'x': return y16t_idx_foreach_x(fh, value, printall_fecb, 0);
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case 'y': return y16t_idx_foreach_y(fh, value, printall_fecb, 0);
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default: return -1;
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}
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}
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