From cf84b9fa46e53c37af2dcb8532e56ab1e7b72e50 Mon Sep 17 00:00:00 2001
From: Ringo Watanabe <flandre@chiru.no>
Date: Sat, 1 Dec 2018 23:17:10 +0000
Subject: [PATCH] start hashtable

---
 build/.gitkeep         |  0
 include/hashtable.h    | 15 ++++++++++++
 include/internal/crc.h | 11 +++++++++
 obj/.gitkeep           |  0
 src/crc.c              | 52 ++++++++++++++++++++++++++++++++++++++++++
 src/hash.c             | 33 +++++++++++++++++++++++++++
 6 files changed, 111 insertions(+)
 create mode 100644 build/.gitkeep
 create mode 100644 include/hashtable.h
 create mode 100644 include/internal/crc.h
 create mode 100644 obj/.gitkeep
 create mode 100644 src/crc.c
 create mode 100644 src/hash.c

diff --git a/build/.gitkeep b/build/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/include/hashtable.h b/include/hashtable.h
new file mode 100644
index 0000000..b9f5401
--- /dev/null
+++ b/include/hashtable.h
@@ -0,0 +1,15 @@
+#ifndef _HASHTABLE_H
+
+#define H_DEFAULT_BLOCKSIZE 255
+
+struct _h_kvpair_t {
+	unsigned int crc32;
+	unsigned char data[];
+};
+
+typedef struct {
+	list_t* back;
+	size_t keysize;
+} hashtable_t;
+
+#endif /* _HASHTABLE_H */
diff --git a/include/internal/crc.h b/include/internal/crc.h
new file mode 100644
index 0000000..8923954
--- /dev/null
+++ b/include/internal/crc.h
@@ -0,0 +1,11 @@
+#ifndef _CRC_H
+#define _CRC_H
+#include <stdint.h>
+#include <stdatomic.h>
+
+#define _H_CRC_TABLE_SIZE 256
+#define _H_CRC_ITERATIONS 8
+
+unsigned long _h_crc32(unsigned long seed, const unsigned char* buffer,unsigned int len);
+
+#endif /* _CRC_H */
diff --git a/obj/.gitkeep b/obj/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/src/crc.c b/src/crc.c
new file mode 100644
index 0000000..c5e484b
--- /dev/null
+++ b/src/crc.c
@@ -0,0 +1,52 @@
+#include <internal/crc.h>
+
+static const uint32_t __h_crc_poly = 0xedb88320u;
+
+static uint32_t __h_crc_table[_H_CRC_TABLE_SIZE];
+static _Atomic volatile int __h_crc_initialised=0;
+
+static _Atomic volatile int __initialising=0;
+
+static uint32_t* __h_crc_create_table(uint32_t* table, uint32_t poly)
+{
+	register int i=0;
+	for(;i<_H_CRC_TABLE_SIZE;i++)
+	{
+		register int j=0;
+		uint32_t e = (uint32_t)i;
+		for(;j<_H_CRC_ITERATIONS;j++)
+		{
+			if( (e&1) == 1)
+				e = (e>>1) ^ poly;
+			else e = e>>1;
+		}
+		table[i] = e;
+	}
+	return table;
+}
+
+static uint32_t __h_crc_calc(uint32_t* table, uint32_t seed,  const unsigned char* buffer, int len)
+{
+	uint32_t crc= seed;
+	register int i=0;
+	for(;i<len;i++)
+	{
+		crc = (crc>>8) ^ table[(buffer[i] ^ crc) & 0xff];
+	}
+	return crc;
+}
+
+unsigned long _h_crc32(unsigned long seed, const unsigned char* buffer,unsigned int len)
+{
+	while(__initialising) (void)0;
+	
+	if(!__h_crc_initialised)
+	{
+		__initialising=1;
+		__h_crc_create_table(__h_crc_table,__h_crc_poly);
+		__h_crc_initialised=1;
+		__initialising=0;
+		
+	}
+	return ~__h_crc_calc(__h_crc_table, (uint32_t) seed, buffer, (int)len);
+}
diff --git a/src/hash.c b/src/hash.c
new file mode 100644
index 0000000..fd7dfa2
--- /dev/null
+++ b/src/hash.c
@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <list.h>
+#include <unistd.h>
+
+#include <internal/crc.h>
+
+#include <hashtable.h>
+
+int32_t _h_getid(void* key, unsigned long* sum, size_t keysize, size_t blocksize)
+{
+	return (int32_t)((*sum = _h_crc32(0xffffffffu, key, keysize)) % blocksize);
+}
+
+hashtable_t* h_create(size_t keytype, size_t valuetype, size_t blocksize)
+{
+	hashtable_t* proto = (hashtable_t*)malloc(sizeof(hashtable_t));
+		
+	proto->back = l_create(sizeof(struct _h_kvpair_t)+keytype+valuetype, blocksize);
+	proto->keysize = keytype;
+
+	return proto;
+}
+
+void h_add(hashtable_t* hash, void* key, void* value)
+{
+	unsigned long crc32;
+	int32_t id = _h_getid(key, &crc32, hash->keysize, hash->back->blocksize);
+	
+	//TODO: search through blocks as pages for empty id match
+	
+}