-- C module extracted from ITU-T X.667 (10/2012)
#include "copyrt.h" #include <string.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #include "sysdep.h" #ifndef _WINDOWS_ #include <arpa/inet.h> #endif #include "uuid.h" /* various forward declarations */ static int read_state(unsigned16 *clockseq, uuid_time_t *timestamp, uuid_node_t *node); static void write_state(unsigned16 clockseq, uuid_time_t timestamp, uuid_node_t node); static void format_uuid_v1(uuid_t *uuid, unsigned16 clockseq, uuid_time_t timestamp, uuid_node_t node); static void format_uuid_v3(uuid_t *uuid, unsigned char hash[16]); static void get_current_time(uuid_time_t *timestamp); static unsigned16 true_random(void); /* uuid_create -- generator a UUID */ int uuid_create(uuid_t *uuid) { uuid_time_t timestamp, last_time; unsigned16 clockseq; uuid_node_t node; uuid_node_t last_node; int f; /* acquire system-wide lock so we''re alone */ LOCK; /* get time, node identifier, saved state from non-volatile storage */ get_current_time(×tamp); get_ieee_node_identifier(&node); f = read_state(&clockseq, &last_time, &last_node); /* if no NV state, or if clock went backwards, or node identifier changed (e.g., new network card) change clockseq */ if (!f || memcmp(&node, &last_node, sizeof node)) clockseq = true_random(); else if (timestamp < last_time) clockseq++; /* save the state for next time */ write_state(clockseq, timestamp, node); UNLOCK; /* stuff fields into the UUID */ format_uuid_v1(uuid, clockseq, timestamp, node); return 1; } /* format_uuid_v1 -- make a UUID from the timestamp, clockseq, and node identifier */ void format_uuid_v1(uuid_t* uuid, unsigned16 clock_seq, uuid_time_t timestamp, uuid_node_t node) { /* Construct a version 1 uuid with the information we''ve gathered plus a few constants. */ uuid->time_low = (unsigned long)(timestamp & 0xFFFFFFFF); uuid->time_mid = (unsigned short)((timestamp >> 32) & 0xFFFF); uuid->time_hi_and_version = (unsigned short)((timestamp >> 48) & 0x0FFF); uuid->time_hi_and_version |= (1 << 12); uuid->clock_seq_low = clock_seq & 0xFF; uuid->clock_seq_hi_and_reserved = (clock_seq & 0x3F00) >> 8; uuid->clock_seq_hi_and_reserved |= 0x80; memcpy(&uuid->node, &node, sizeof uuid->node); } /* data type for UUID generator persistent state */ typedef struct { uuid_time_t ts; /* saved timestamp */ uuid_node_t node; /* saved node identifier */ unsigned16 cs; /* saved Clock Sequence */ } uuid_state; static uuid_state st; /* read_state -- read UUID generator state from non-volatile store */ int read_state(unsigned16 *clockseq, uuid_time_t *timestamp, uuid_node_t *node) { static int inited = 0; FILE *fp; /* only need to read state once per boot */ if (!inited) { fp = fopen("state", "rb"); if (fp == NULL) return 0; fread(&st, sizeof st, 1, fp); fclose(fp); inited = 1; } *clockseq = st.cs; *timestamp = st.ts; *node = st.node; return 1; } /* write_state -- save UUID generator state back to non-volatile storage */ void write_state(unsigned16 clockseq, uuid_time_t timestamp, uuid_node_t node) { static int inited = 0; static uuid_time_t next_save; FILE* fp; if (!inited) { next_save = timestamp; inited = 1; } /* always save state to volatile shared state */ st.cs = clockseq; st.ts = timestamp; st.node = node; if (timestamp >= next_save) { fp = fopen("state", "wb"); fwrite(&st, sizeof st, 1, fp); fclose(fp); /* schedule next save for 10 seconds from now */ next_save = timestamp + (10 * 10 * 1000 * 1000); } } /* get-current_time -- get time as 60-bit 100ns ticks since UUID epoch. Compensate for the fact that real clock resolution is less than 100ns. */ void get_current_time(uuid_time_t *timestamp) { static int inited = 0; static uuid_time_t time_last; static unsigned16 uuids_this_tick; uuid_time_t time_now; if (!inited) { get_system_time(&time_now); uuids_this_tick = UUIDS_PER_TICK; inited = 1; } for ( ; ; ) { get_system_time(&time_now); /* if clock reading changed since last UUID generated, */ if (time_last != time_now) { /* reset count of uuids gen''d with this clock reading */ uuids_this_tick = 0; time_last = time_now; break; } if (uuids_this_tick < UUIDS_PER_TICK) { uuids_this_tick++; break; } /* going too fast for our clock; spin */ } /* add the count of uuids to low order bits of the clock reading */ *timestamp = time_now + uuids_this_tick; } /* true_random -- generate a crypto-quality random number. **This sample doesn''t do that.** */ static unsigned16 true_random(void) { static int inited = 0; uuid_time_t time_now; if (!inited) { get_system_time(&time_now); time_now = time_now / UUIDS_PER_TICK; srand((unsigned int)(((time_now >> 32) ^ time_now) & 0xffffffff)); inited = 1; } return rand(); } /* uuid_create_from_name -- create a UUID using a "name" from a "name space" */ void uuid_create_from_name(uuid_t *uuid, uuid_t nsid, void *name, int namelen) { MD5_CTX c; unsigned char hash[16]; uuid_t net_nsid; /* put name space identifier in network byte order so it hashes the same no matter what endian machine we''re on */ net_nsid = nsid; htonl(net_nsid.time_low); htons(net_nsid.time_mid); htons(net_nsid.time_hi_and_version); MD5Init(&c); MD5Update(&c, &net_nsid, sizeof net_nsid); MD5Update(&c, name, namelen); MD5Final(hash, &c); /* the hash is in network byte order at this point */ format_uuid_v3(uuid, hash); } /* format_uuid_v3 -- make a UUID from a (pseudo)random 128-bit number */ void format_uuid_v3(uuid_t *uuid, unsigned char hash[16]) { /* convert UUID to local byte order */ memcpy(uuid, hash, sizeof *uuid); ntohl(uuid->time_low); ntohs(uuid->time_mid); ntohs(uuid->time_hi_and_version); /* put in the variant and version bits */ uuid->time_hi_and_version &= 0x0FFF; uuid->time_hi_and_version |= (3 << 12); uuid->clock_seq_hi_and_reserved &= 0x3F; uuid->clock_seq_hi_and_reserved |= 0x80; } /* uuid_compare -- Compare two UUID''s "lexically" and return */ #define CHECK(f1, f2) if (f1 != f2) return f1 < f2 ? -1 : 1; int uuid_compare(uuid_t *u1, uuid_t *u2) { int i; CHECK(u1->time_low, u2->time_low); CHECK(u1->time_mid, u2->time_mid); CHECK(u1->time_hi_and_version, u2->time_hi_and_version); CHECK(u1->clock_seq_hi_and_reserved, u2->clock_seq_hi_and_reserved); CHECK(u1->clock_seq_low, u2->clock_seq_low) for (i = 0; i < 6; i++) { if (u1->node[i] < u2->node[i]) return -1; if (u1->node[i] > u2->node[i]) return 1; } return 0; } #undef CHECK