51Degrees Device Detection C/C++  4.5

A device detection library that is used natively or by 51Degrees products

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Hash/OfflineProcessing.c

Provides an example of processing a YAML file containing evidence for device detection.

Provides an example of processing a YAML file containing evidence for device detection.There are 20,000 examples in the supplied file of evidence representing HTTP Headers. For example:

header.user-agent: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.102 Safari/537.36'

header.sec-ch-ua: '" Not A;Brand";v="99", "Chromium";v="98", "Google Chrome";v="98"'

header.sec-ch-ua-full-version: '"98.0.4758.87"'

header.sec-ch-ua-mobile: '?0'

header.sec-ch-ua-platform: '"Android"'

We create a resource manager and results hash to read the data and find out about the associated device, we write this data to a YAML formatted output stream.

As well as explaining the basic operation of offline processing using the defaults, for advanced operation this example can be used to experiment with tuning device detection for performance and predictive power using Performance Profile, Graph and Difference and Drift settings.

This example is available in full on GitHub

/* *********************************************************************

* This Original Work is copyright of 51 Degrees Mobile Experts Limited.

* Copyright 2026 51 Degrees Mobile Experts Limited, Davidson House,

* Forbury Square, Reading, Berkshire, United Kingdom RG1 3EU.

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*

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// Include ExmapleBase.h before others as it includes Windows 'crtdbg.h'

// which requires to be included before 'malloc.h'.

#include "ExampleBase.h"

#include "../../../../src/dd/hash/hash.h"

#include "../../../../src/common/textfile.h"

#include "../../../../src/dd/hash/fiftyone.h"

static const char *dataDir = "data/device-detection";

// In this example, by default, the 51degrees "Lite" file needs to be somewhere in the

// project space, or you may specify another file as a command line parameter.

//

// Note that the Lite data file is only used for illustration, and has limited accuracy

// and capabilities. Find out about the Enterprise data file on our pricing page:

// /pricing?utm_source=code&utm_medium=example&utm_campaign=51degrees-cxx&utm_content=examples-c-hash-offlineprocessing.c&utm_term=top

static const char *dataFileName = "51Degrees-LiteV4.1.hash";

// This file contains the 20,000 most commonly seen combinations of header values

// that are relevant to device detection. For example, User-Agent and UA-CH headers.

static const char *evidenceFileName = "20000 Evidence Records.yml";

// Returned by main. Set to 1 when the data file cannot be used.

static int exitCode = 0;

static char valueBuffer[1024] = "";

static const size_t valueBufferLength = sizeof(valueBuffer) / sizeof(valueBuffer[0]);

// We use the low memory profile as its performance is sufficient for this

// example. See the documentation for more detail on this and other

// configuration options:

// /documentation/_device_detection__features__performance_options.html?utm_source=code&utm_medium=example&utm_campaign=51degrees-cxx&utm_content=examples-c-hash-offlineprocessing.c&utm_term=top

// /documentation/_pipeline_api__features__automatic_datafile_updates.html?utm_source=code&utm_medium=example&utm_campaign=51degrees-cxx&utm_content=examples-c-hash-offlineprocessing.c&utm_term=top

// /documentation/_pipeline_api__features__usage_sharing.html?utm_source=code&utm_medium=example&utm_campaign=51degrees-cxx&utm_content=examples-c-hash-offlineprocessing.c&utm_term=top

// #define CONFIG fiftyoneDegreesHashInMemoryConfig

// #define CONFIG fiftyoneDegreesHashHighPerformanceConfig

#define CONFIG fiftyoneDegreesHashLowMemoryConfig

// #define CONFIG fiftyoneDegreesHashBalancedConfig

// #define CONFIG fiftyoneDegreesHashBalancedTempConfig

typedef struct t_offline_processing_state {

FILE *outputFile;

FILE *outputLog;

ResultsHash *results;

} offlineProcessState;

static void outputDeviceId(

ResultsHash *results,

const char *name,

FILE *output) {

char buffer[50];

EXCEPTION_CREATE

HashGetDeviceIdFromResults (results, buffer, 50, exception);

EXCEPTION_THROW

fprintf(output, "%s: %s\n", name, buffer);

}

static void outputValue(

ResultsHash *results,

const char *name,

const char* propertyName,

FILE *output) {

DataSetHash* dataset = (DataSetHash*)results->b.b.dataSet;

int requiredIndex = PropertiesGetRequiredPropertyIndexFromName(

dataset->b.b.available,

propertyName);

EXCEPTION_CREATE;

// If a value has not been set then trying to access the value will

// result in an exception.

if (ResultsHashGetHasValues(

results, requiredIndex, exception)) {

ResultsHashGetValuesString(

results,

propertyName,

valueBuffer,

valueBufferLength,

(char* const)",",

exception);

EXCEPTION_THROW;

}

else {

// A no value message can also be obtained. This message describes why

// the value has not been set.

fiftyoneDegreesResultsNoValueReason reason =

ResultsHashGetNoValueReason(results, requiredIndex, exception);

EXCEPTION_THROW;

snprintf(valueBuffer, valueBufferLength, "Unknown (%s)", ResultsHashGetNoValueReasonMessage(reason));

}

fprintf(output, "%s: %s\n", name, valueBuffer);

}

static void analyse(

ResultsHash* results,

EvidenceKeyValuePairArray* evidence,

FILE* outputFile) {

// Information required for detection is called "evidence"

// and usually consists of a number of HTTP Header field

// values, in this case represented by a

// Object of header name/value entries.

// list the evidence

fprintf(outputFile, "---\n");

for (uint32_t i = 0; i < evidence->count; i++) {

EvidenceKeyValuePair e = evidence->items[i];

fprintf(outputFile,

"%s%s: %s\n",

EvidencePrefixString(e.prefix),

e.item.key,

e.item.value);

}

EXCEPTION_CREATE

ResultsHashFromEvidence(results, evidence, exception);

EXCEPTION_THROW

outputValue(results, "device.ismobile", "IsMobile", outputFile);

outputValue(results, "device.platformname", "PlatformName", outputFile);

outputValue(results, "device.platformversion", "PlatformVersion", outputFile);

outputValue(results, "device.browsername", "BrowserName", outputFile);

outputValue(results, "device.browserversion", "BrowserVersion", outputFile);

// DeviceId is a unique identifier for the combination of hardware, operating

// system, browser and crawler that has been detected.

// Our device detection solution uses machine learning to find the optimal

// way to identify devices based on the real-world evidence values that we

// observe each day.

// As this changes over time, the result of detection can potentially change

// as well. By storing the device id, we can use this as a lookup in future

// rather than performing detection with the original evidence again.

// Do this by passing an evidence entry with:

// key = query.51D_ProfileIds

// value = [the device id]

// This is much faster and avoids the potential for getting a different

// result.

outputDeviceId(results, "device.deviceid", outputFile);

}

static void process(KeyValuePair *pairs, uint16_t size, void *state) {

EXCEPTION_CREATE;

offlineProcessState *offline = (offlineProcessState*)state;

// Create an evidence collection and add the evidence to the collection

EvidenceKeyValuePairArray* evidenceArray = EvidenceCreate(size);

for (uint32_t i = 0; i < size; i++) {

// Get prefix

EvidencePrefixMap *prefixMap = EvidenceMapPrefix(pairs[i].key);

if (prefixMap) {

// Add the evidence as string

EvidenceAddString(

evidenceArray,

prefixMap->prefixEnum,

pairs[i].key + prefixMap->prefixLength,

pairs[i].value);

}

}

analyse(

offline->results,

evidenceArray,

offline->outputFile);

// Ensure the evidence collection is freed after used

EvidenceFree(evidenceArray);

}

void run(

ResourceManager *manager,

const char *evidenceFilePath,

const char *outputFilePath,

FILE *output) {

char buffer[1000];

offlineProcessState state;

// Open a fresh data file for writing the output to.

FileDelete(outputFilePath);

state.outputFile = fopen(outputFilePath, "w");

if (state.outputFile == NULL) {

fprintf(output, "Could not open file %s for write\n", outputFilePath);

return;

}

state.outputLog = output;

// Get the results and data set from the manager. Use a higher closest

// number of signatures than the default because performance is less

// important for offline processing and expanding the number of

// alternatives evaluated can lead to a better result.

state.results = ResultsHashCreate(manager, 10);

KeyValuePair pair[10];

char key[10][500];

char value[10][1000];

for (int i = 0; i < 10; i++) {

pair[i].key = key[i];

pair[i].keyLength = 500;

pair[i].value = value[i];

pair[i].valueLength = 1000;

}

// Perform offline processing.

YamlFileIterate(

evidenceFilePath,

buffer,

sizeof(buffer),

pair,

10,

&state,

process

);

fprintf(state.outputFile, "...\n");

fclose(state.outputFile);

fprintf(output, "Output Written to %s\n", outputFilePath);

DataSetHash* dataset = (DataSetHash *)state.results->b.b.dataSet;

fiftyoneDegreesExampleCheckDataFile(dataset);

// Free the memory used by the results instance.

ResultsHashFree(state.results);

}

static void reportStatus(

StatusCode status,

const char* fileName) {

const char *message = StatusGetMessage(status, fileName);

printf("%s\n", message);

Free((void*)message);

}

void fiftyoneDegreesOfflineProcessingRun(

const char *dataFilePath,

const char *evidenceFilePath,

const char *outputFilePath,

const char *requiredProperties,

ConfigHash config,

FILE* output) {

EXCEPTION_CREATE;

// Set concurrency to ensure sufficient shared resources available.

config.nodes.concurrency =

config.profiles.concurrency =

config.profileOffsets.concurrency =

config.rootNodes.concurrency =

config.values.concurrency =

config.strings.concurrency = 1;

// If time can be sacrificed for a more thorough analysis of the different

// options then increase the closestSignatures value. More permutations

// will be considered the higher the number.

// config.closestSignatures = 50000;

// Set the required properties for the output file.

PropertiesRequired properties = PropertiesDefault;

properties.string = requiredProperties;

// Set the User-Agent update so that we can output the sub strings found

// and not the entire User-Agent.

config.b.updateMatchedUserAgent = true;

ResourceManager manager;

StatusCode status = HashInitManagerFromFile(

&manager,

&config,

&properties,

dataFilePath,

exception);

printf("%s\n", dataFilePath);

if (status != SUCCESS) {

reportStatus(status, dataFilePath);

exitCode = 1;

}

else {

// Process the evidence writing the results to the output path.

run(&manager, evidenceFilePath, outputFilePath, output);

// Free the memory used by the data set.

ResourceManagerFree(&manager);

fprintf(output, "Processing complete. See results in: '%s'", outputFilePath);

}

}

void fiftyoneDegreesExampleCOfflineProcessingRun(ExampleParameters *params) {

// Call the actual function.

fiftyoneDegreesOfflineProcessingRun(

params->dataFilePath,

params->evidenceFilePath,

params->outputFilePath,

params->propertiesString,

*params->config,

params->output);

}

#ifndef TEST

static const char* getBaseName(const char* path) {

for (size_t i = strlen(path) - 1; i >= 0; i--) {

if (path[i] == '\\' || path[i] == '/') {

// Check if there is a basename

if (i == (strlen(path) - 1)) {

return NULL;

}

return path + i + 1;

}

}

return path;

}

int main(int argc, char* argv[]) {

StatusCode status = SUCCESS;

char dataFilePath[FILE_MAX_PATH];

char evidenceFilePath[FILE_MAX_PATH];

char outputFilePath[FILE_MAX_PATH];

// Set data file path

if (argc > 1) {

strcpy(dataFilePath, argv[1]);

}

else {

status = fiftyoneDegreesExampleGetFilePath(

dataDir,

dataFileName,

dataFilePath,

sizeof(dataFilePath));

if (status != SUCCESS) {

printf(("Failed to find a device detection "

"data file. Make sure the data submodule is there, "

"by running `git submodule update --init data`, and "

"run this example again to download the file."));

fgetc(stdin);

return 1;

}

}

// Set evidence file path

if (argc > 2) {

strcpy(evidenceFilePath, argv[2]);

}

else {

status = fiftyoneDegreesExampleGetFilePath(

dataDir,

evidenceFileName,

evidenceFilePath,

sizeof(evidenceFilePath));

if (status != SUCCESS) {

reportStatus(status, evidenceFilePath);

fgetc(stdin);

return 1;

}

}

// Set output file path

if (argc > 3) {

strcpy(outputFilePath, argv[3]);

}

else {

const char* baseName = getBaseName(evidenceFilePath);

if (baseName == NULL) {

printf("Invalid evidence file path.\n");

fgetc(stdin);

return 1;

}

size_t cpySize = baseName - evidenceFilePath;

strncpy(outputFilePath, evidenceFilePath, cpySize);

strcpy(outputFilePath + cpySize, "offline-processing-output.yml");

}

ConfigHash config = CONFIG;

ExampleParameters params;

params.dataFilePath = dataFilePath;

params.evidenceFilePath = evidenceFilePath;

params.outputFilePath = outputFilePath;

params.propertiesString = argc > 4 ? argv[4] : "";

params.config = &config;

params.output = stdout;

// Run the example

fiftyoneDegreesExampleMemCheck(

&params,

fiftyoneDegreesExampleCOfflineProcessingRun);

// Wait for a character to be pressed.

fgetc(stdin);

return exitCode;

}

#endif

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