vnlog.c

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
#include <string.h>

#include "vnlog-base64.h"

#define VNLOG_C
#include "vnlog.h"

#define ERR(fmt, ...) do {                                              \
        fprintf(stderr, "FATAL ERROR! %s: %s(): " fmt "\n", __FILE__, __func__, ## __VA_ARGS__); \
        exit(1);                                                        \
    } while(0)

void _vnlog_init_session_ctx( struct vnlog_context_t* ctx,
                              int Nfields);

// VNLOG_N_FIELDS is unknown here so the vnlog_context_t structure has 0
// elements. I dynamically allocate it later with the proper size
static struct vnlog_context_t* get_global_context(int Nfields)
{
    static struct vnlog_context_t* ctx;

    if(!ctx)
    {
        if(Nfields < 0)
            ERR("Creating a global context not at the start");
        ctx = malloc(sizeof(struct vnlog_context_t) +
                     Nfields * sizeof(ctx->fields[0]));
        if(!ctx) ERR("Couldn't allocate context with %d fields", Nfields);

        _vnlog_init_session_ctx(ctx, Nfields);
    }
    return ctx;
}



static void _vnlog_set_output_FILE__ctx_exists(struct vnlog_context_t* ctx, FILE* fp)
{
    if(ctx->root->_fp)
        ERR("fp is already set");
    if( ctx->root->_emitted_something )
        ERR("Can only change the output at the start");

    ctx->root->_fp = fp;
}
// This is part of the CURRENT ABI. The user calls vnlog_set_output_FILE(), this
// is expanded by the preprocessor to _vnlog_set_output_FILE()
void _vnlog_set_output_FILE(struct vnlog_context_t* ctx, FILE* fp, int Nfields)
{
    if( ctx == NULL )
        ctx = get_global_context(Nfields);
    _vnlog_set_output_FILE__ctx_exists(ctx, fp);
}
// This is for legacy compatibility. With today's vnlog, user calls to
// vnlog_set_output_FILE() are expanded to _vnlog_set_output_FILE() by the
// preprocessor, so THIS symbol is not used, and does not conflict. But old
// binaries could call vnlog_set_output_FILE() directly, so I provide that here,
// with the exact old implementation
void vnlog_set_output_FILE(struct vnlog_context_t* ctx, FILE* fp)
{
    _vnlog_set_output_FILE__ctx_exists(ctx, fp);
}

static void check_fp(struct vnlog_context_t* ctx)
{
    if(!ctx->root->_fp)
        _vnlog_set_output_FILE__ctx_exists(ctx, stdout);
}
static void _emit(struct vnlog_context_t* ctx, const char* string)
{
    fprintf(ctx->root->_fp, "%s", string);
    ctx->root->_emitted_something = true;
}

static void _emit_field(struct vnlog_context_t* ctx, int i)
{
    if( ctx->fields[i].binptr == NULL )
        // plain ascii field
        _emit(ctx, ctx->fields[i].c);
    else
    {
        // binary field. Encode with base64 first
        char out_base64[vnlog_base64_dstlen_to_encode(ctx->fields[i].binlen)];
        vnlog_base64_encode( out_base64, sizeof(out_base64),
                             ctx->fields[i].binptr, ctx->fields[i].binlen );
        _emit(ctx, out_base64);
    }
}

static void emit(struct vnlog_context_t* ctx, const char* string)
{
    check_fp(ctx);
    _emit(ctx, string);
}

void _vnlog_printf(struct vnlog_context_t* ctx, int Nfields, const char* fmt, ...)
{
    if( ctx == NULL ) ctx = get_global_context(Nfields);
    check_fp(ctx);
    va_list ap;
    va_start(ap, fmt);
    vfprintf(ctx->root->_fp, fmt, ap);
    va_end(ap);

    ctx->root->_emitted_something = true;
}

void _vnlog_flush(struct vnlog_context_t* ctx, int Nfields)
{
    if( ctx == NULL ) ctx = get_global_context(Nfields);
    check_fp(ctx);
    fflush(ctx->root->_fp);
}

static void flush(struct vnlog_context_t* ctx)
{
    fflush(ctx->root->_fp);
}

void _vnlog_clear_fields_ctx(struct vnlog_context_t* ctx, int Nfields, bool do_free_binary)
{
    ctx->line_has_any_values = false;
    for(int i=0; i<Nfields; i++)
    {
        ctx->fields[i].c[0]   = '-';
        ctx->fields[i].c[1]   = '\0';

        // Here the idea is that once I emit the field I deallocate. This is
        // inefficient, but allows some things to be simple. For instance I can
        // use NULL to recognize empty binary fields. The vast majority of these
        // data files will have no binary fields, and this simplicity is good
        if(do_free_binary)
            free(ctx->fields[i].binptr);
        ctx->fields[i].binptr = NULL;
    }
}

void _vnlog_init_session_ctx( struct vnlog_context_t* ctx, int Nfields)
{
    if( ctx == NULL )
        ERR("Can't init a NULL context");

    // zero out the context, and set its root to point to itself
    *ctx = (struct vnlog_context_t){ .root = ctx };

    _vnlog_clear_fields_ctx( ctx, Nfields, false );
}

void _vnlog_init_child_ctx(      struct vnlog_context_t* ctx,
                                 const struct vnlog_context_t* ctx_src,
                                 int Nfields)
{
    if( ctx     == NULL ) ERR("Can't init a NULL context");
    if( ctx_src == NULL ) ctx_src = get_global_context(Nfields);

    if( !ctx_src->root->_legend_finished )
        ERR("Cannot create children contexts before writing a legend. Hard to keep state consistent otherwise.");


    // Copy all the context except for the flexible array at the end. The root
    // context pointer is copied as well, which is the desired behavior: this
    // child has the same root node as the parent
    *ctx = *ctx_src;

    // reset the flexible array
    _vnlog_clear_fields_ctx( ctx, Nfields, false );
}

void _vnlog_free_ctx( struct vnlog_context_t* ctx, int Nfields )
{
    for(int i=0; i<Nfields; i++)
    {
        free(ctx->fields[i].binptr);
        ctx->fields[i].binptr = NULL;
    }
}

void _vnlog_emit_legend(struct vnlog_context_t* ctx, const char* legend, int Nfields)
{
    if( ctx == NULL ) ctx = get_global_context(Nfields);

    if( ctx->root->_legend_finished )
        ERR("already have a legend");
    ctx->root->_legend_finished = true;

    emit(ctx, legend);
    flush(ctx);
}

static bool is_field_null(const vnlog_field_t* field)
{
    return field->binptr == NULL && field->c[0] == '-' && field->c[1] == '\0';
}

static struct vnlog_context_t*
set_field_prelude(struct vnlog_context_t* ctx,
                  const char* fieldname, int idx)
{
    if( ctx == NULL ) ctx = get_global_context(-1);

    if(!ctx->root->_legend_finished)
        ERR("need a legend to do this");
    if(!is_field_null(&ctx->fields[idx]))
        ERR("Field '%s' already set. Old value: '%s'",
            fieldname, ctx->fields[idx].c);
    ctx->line_has_any_values = true;

    return ctx;
}


#define DEFINE_SET_FIELD_FUNCTION(type, typename, fmt)                  \
void                                                                    \
_vnlog_set_field_value_ ## typename(struct vnlog_context_t* ctx,        \
                                    const char* fieldname, int idx,     \
                                    type arg)                           \
{                                                                       \
    ctx = set_field_prelude(ctx, fieldname, idx);                       \
    if( (int)sizeof(ctx->fields[0].c) <=                                \
        snprintf(ctx->fields[idx].c, sizeof(ctx->fields[0].c), fmt, arg) ) \
    {                                                                   \
        ERR("Field size exceeded for field '%s'", fieldname);           \
    }                                                                   \
}

VNLOG_TYPES( DEFINE_SET_FIELD_FUNCTION )
#undef DEFINE_SET_FIELD_FUNCTION

void
_vnlog_set_field_value_binary(struct vnlog_context_t* ctx,
                              const char* fieldname __attribute__((unused)), int idx,
                              const void* data, int len)
{
    ctx = set_field_prelude(ctx, fieldname, idx);

    // Here I allocate the memory for the data, and copy into it. The idea is
    // that once I emit the field I deallocate. This is inefficient, but allows
    // some things to be simple. For instance I can use NULL to recognize empty
    // binary fields. The vast majority of these data files will have no binary
    // fields, and this simplicity is good
    ctx->fields[idx].binlen = len;
    ctx->fields[idx].binptr = realloc(ctx->fields[idx].binptr, len);
    memcpy(ctx->fields[idx].binptr, data, len);
}

void _vnlog_emit_record(struct vnlog_context_t* ctx, int Nfields)
{
    if( ctx == NULL ) ctx = get_global_context(-1);

    if(!ctx->root->_legend_finished)
        ERR("need a legend to do this");

    if(!ctx->line_has_any_values)
        ERR("Tried to emit a log line without any values being set");

    check_fp(ctx);

    flockfile(ctx->root->_fp);
    {
        for(int i=0; i<Nfields-1; i++)
        {
            _emit_field(ctx, i);
            _emit(ctx, " ");
        }
        _emit_field(ctx, Nfields-1);
        _emit(ctx, "\n");
    }
    funlockfile(ctx->root->_fp);

    _vnlog_clear_fields_ctx(ctx, Nfields, true);
}