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package c
/*
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#define MAX_DEPTH 100
#define BRANCH_PAGE 1
// These types MUST have the same layout as their corresponding Go types
typedef int64_t pgid;
typedef struct page {
pgid id;
uint16_t flags;
uint16_t count;
uint32_t overflow;
} page;
typedef struct branch_elem {
uint32_t pos;
uint32_t ksize;
pgid page;
} branch_elem;
typedef struct leaf_elem {
uint32_t flags;
uint32_t pos;
uint32_t ksize;
uint32_t vsize;
} leaf_elem;
// private types
typedef struct elem_ref {
page *page;
uint16_t index;
} elem_ref;
// public types
typedef struct bolt_val {
uint32_t size;
void *data;
} bolt_val;
typedef struct bolt_cursor {
void *data;
pgid root;
size_t pgsz;
unsigned int stackp;
elem_ref stack[MAX_DEPTH];
} bolt_cursor;
// int bolt_cursor_seek(bolt_cursor *c, bolt_val *key, bolt_val *actual_key, bolt_val *value)
// private functions
// Returns a page pointer from a page identifier.
page *get_page(bolt_cursor *c, pgid id) {
return (page *)(c->data + (c->pgsz * id));
}
// Returns the leaf element at a given index on a given page.
branch_elem *branch_page_element(page *p, uint16_t index) {
branch_elem *elements = (branch_elem*)((void*)(p) + sizeof(page));
return &elements[index];
}
// Returns the leaf element at a given index on a given page.
leaf_elem *leaf_page_element(page *p, uint16_t index) {
leaf_elem *elements = (leaf_elem*)((void*)(p) + sizeof(page));
return &elements[index];
}
// Sets the key and value for a leaf element to a bolt value.
void key_value(leaf_elem *leaf, bolt_val *key, bolt_val *value) {
key->size = leaf->ksize;
key->data = ((void*)leaf) + leaf->pos;
value->size = leaf->vsize;
value->data = key->data + key->size;
}
// Traverses from the current stack position down to the first leaf element.
int bolt_cursor_first_leaf(bolt_cursor *c, bolt_val *key, bolt_val *value) {
elem_ref *ref = &(c->stack[c->stackp]);
branch_elem *branch;
while (ref->page->flags & BRANCH_PAGE) {
branch = branch_page_element(ref->page,ref->index);
c->stackp++;
ref = &c->stack[c->stackp];
ref->index = 0;
ref->page = get_page(c, branch->page);
};
key_value(leaf_page_element(ref->page,ref->index), key, value);
return 0;
}
// public functions
void bolt_cursor_init(bolt_cursor *c, void *data, size_t pgsz, pgid root) {
c->data = data;
c->root = root;
c->pgsz = pgsz;
}
int bolt_cursor_first(bolt_cursor *c, bolt_val *key, bolt_val *value) {
leaf_elem *leaf;
elem_ref *ref;
// reset stack to initial state
c->stackp = 0;
ref = &(c->stack[c->stackp]);
ref->page = get_page(c, c->root);
ref->index = 0;
// get current leaf element
return bolt_cursor_first_leaf(c, key, value);
}
int bolt_cursor_next(bolt_cursor *c, bolt_val *key, bolt_val *value) {
elem_ref *ref = &c->stack[c->stackp];
// increment element index
ref->index++;
// if we're past last element pop the stack and repeat
while (ref->index >= ref->page->count ) {
c->stackp--;
ref = &c->stack[c->stackp];
ref->index++;
};
// get current leaf element
return bolt_cursor_first_leaf(c, key, value);
}
*/
import "C"
import (
"fmt"
"os"
"unsafe"
"github.com/boltdb/bolt"
)
// Cursor represents a wrapper around a Bolt C cursor.
type Cursor struct {
C *C.bolt_cursor
}
// NewCursor creates a C cursor from a Bucket.
func NewCursor(b *bolt.Bucket) *Cursor {
info := b.Tx().DB().Info()
root := b.Root()
c := &Cursor{C: new(C.bolt_cursor)}
C.bolt_cursor_init(c.C, unsafe.Pointer(&info.Data[0]), C.size_t(info.PageSize), C.pgid(root))
return c
}
// first moves the cursor to the first element and returns the key and value.
// Returns a nil key if there are no elements.
func first(c *Cursor) (key, value []byte) {
var k, v C.bolt_val
C.bolt_cursor_first(c.C, &k, &v)
return C.GoBytes(k.data, C.int(k.size)), C.GoBytes(v.data, C.int(v.size))
}
// next moves the cursor to the next element and returns the key and value.
// Returns a nil key if at the end of the bucket.
func next(c *Cursor) (key, value []byte) {
var k, v C.bolt_val
C.bolt_cursor_next(c.C, &k, &v)
return C.GoBytes(k.data, C.int(k.size)), C.GoBytes(v.data, C.int(v.size))
}
func warn(v ...interface{}) {
fmt.Fprintln(os.Stderr, v...)
}
func warnf(msg string, v ...interface{}) {
fmt.Fprintf(os.Stderr, msg+"\n", v...)
}
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